of which communicates with a cannula adapted to the trachea of the animal.

The membrane between the atlas and the occipital bone having been previously exposed and one of the carotid arteries connected with the manometer of the kymograph, observations are taken of the arterial pressure and of the frequency of the pulse. This done the spinal cord is divided at the atlas. Immediately the rate of pulsation is diminished, say from 140 to 100, and after a few seconds the arterial pressure sinks, say from three or four inches, to one or two. Needles are then inserted into the spinal cord, one at the upper edge of the axis, both of which are connected with the secondary coil of Dubois' induction apparatus. At once the heart beats more frequently and vigorously and the mercurial column attains its former level.

The next step in the experiment is the destruction of the cerebrospinal cardiac nerves. These nerves, as you know, reach the heart or leave it either through the vagi or the sympathetic.

The destruction of the nerves is best effected with the galvanic cautery, the action of which is more certain and more easily controlled than any other agent which could be employed. It answers the purpose so completely that in careful subsequent dissection it is found that every nerve is severed. As soon as the destruction of the nerves is effected the spinal cord is again excited, great care being taken that the strength of the current shall be the same as in the previous observation.

There are, however, in these and other respects considerable differences in the results observed in different animals, the conditions of which have not yet been determined.*

Upon another dog under partial anesthesia, he divided with a fine curved scalpel the corpus striatum and optic thalamus on one side, the corpus callosum having previously been cut through. The electrodes were then placed on the convolutions above and behind the sylvian fissure. Contraction resulted, when the current was strong, not only in the fore leg of the opposte side, but also in the hind leg. In another experiment he removed the whole cerebral masses above the four varolii, and applied the electrodes to the surface of the section. Muscular contractions resulted, limited to the fore limbs, right and left.-Lancet, No. 2,630, p. 136.

Handbook Physiological Laboratory.

(165.)-[Some of the following experiments are quoted not to show extreme torture but regardlessness to suffering, as well as the minute character of directions given, to bring them within the capacity of young people.]

* This beautifully simple experiment we owe to Dr. Stricker, with whom I had the pleasure of repeating it here very frequently last summer.-(Medical Times, No. 1,094, pp. 683-4.)

Page 1.-Take the newt out of the water, dry the tail, cut off its end. If no blood comes, squeeze the organ from the root towards the tip until a drop is obtained.

Page 25.—To study the forms of the various cells of the separate layers we may obtain a thin shred from the surface of the tongue or gurus of a mammal by energetically scraping it with a scalpel.

Page 26.-Finally, if we have scraped very energetically with the scalpel, we meet with cells corresponding to the deepest layers. . . . A frog is held by an assistant, its nictitating drawn down, and from the anterior corneal surface a thin layer is scraped wirh a lancetshaped or cataract knife.

Page 34-It is not difficult to remove those structures [network of elastic fibres] even from the living animal. The easiest way is to place the vocal cord for a few minutes in dilute acetic acid, and then to scrape off the epithelium with a lancet-shaped needle-a process which is much facilitated by the previous steeping in the acid.

Page 35.-A frog is held by an assistant in such a way that the bulbus oculi is tense. The membrana nictitans is then drawn back, and the bulb penetrated with a cataract knife, just as in the operation for cataract, at the limbus conjunctivæ next the inner cauthus. The point of the knife is advanced until it approaches the limbus of the opposite side, without puncturing it, and is then carried outwards and upwards, so as to form a flap, consisting of the upper half of the cornea. The extreme edge of the flap must then be seized with the forceps, while the lower half of the cornea is cut away with the aid of scissors curved in the direction of their edge. The cornea is next transferred to a drop of humor aqueous (previously obtained by puncturing the opposite eye), and spread out on the glass slide with the anterior surface uppermost.

Page 38.-Preparations are obtained by stripping off shreds of a cornea (of a rabbit or frog).

The centre of the cornea of a frog, which is held by an assistant in the manner previously described, is firmly cauterised with a pointed stick of lunar caustic. One or two drops of salt solution are then allowed to flow over the cornea to decompose the excess of nitrate of silver. About an hour after the cauterisation the cornea is excised in the manner directed in p. 35. .

It consists in first scraping the cornea of a living frog or small mammal with a sharp cataract knife so as to remove the epithelium completely. After a little practice, and provided the bulb is properly fixed by an assistant, it is not difficult to perform this operation without injuring the substance of the cornea. Thereupon the caustic is two or three times lightly rubbed over the whole surface, after which the eye is washed with saline solution, and the animal is left to itself for twenty or thirty minutes. The cornea is then excised.

Page 44.-If in a rabbit the skin and subcutaneous tissue are divided over the inner (anterior) third of the infraorbital edge, and

the thin membrane which stretches over the infraorbital fossa is severed, it is easy to remove, along with the glandula infraorbitalis, a gelatinous hyaline mass.

If the tail of a very young rat is amputated, and the tip torn asunder from the cut end, a great number of isolated lengths of tendon are obtained.

Page 54. The leg of a water-beetle (hydrophilus) is torn out and its horny covering removed.

Page 60.-One of the hind-legs of a tadpole is amputated at the thigh. The animal is then replaced in water. After forty-eight hours the loosened muscular fibres hang from the stump in long pencils. These are cut off close to the surface of the stump with sharp scissors.

Page 78. In a living or recently-killed rabbit the cornea is excised

close to the limbus.

A silk thread having been passed through the centre of the cornea of rana esculenta and brought out again at the sclerotic ring, the two ends are knotted together. After the thread has remained from five to eight hours the cornea is excised.

Page 97.-In a large frog, secured on its back, the abdominal vein is carefully exposed, under a dissecting lens, in its course up the middle line of the anterior wall of the belly. A ligature is passed round the distal end of the prepared part and tightened.

Page 98. The external jugular of the mammal is then exposed by a sufficient incision and cleared of the surrounding tissue with the aid of dissecting forceps.

Page 108.-A snip is made in the right side of the belly.

The incision is then continued upwards and downwards in such directions as to avoid bleeding.

The muscles are divided in the same vertical line.

The intestine and mesentery are drawn out carefully.

Page 109.-The animal must be curarized as before

the

tongue drawn out by the cornua, around which a thread must be secured

to pins.

Page 113.—In a large or middle-sized rabbit which has been kept from sixteen to twenty hours without food, ten cubic centimetres of a warm five per cent. solution of Prussian blue are injected into the abdominal cavity. After three hours and a half the animal is bled to death by opening the carotid artery, or killed by strangling.

Pages 158 to 162.-The inflammatory changes of the epithelial elements of the cornea may be studied by abrading the epithelium over a limited surface in several frogs, and examining the organ at various periods after the injury. After two or three days, sections may be made by shaving off a portion of the mucous membrane. In the blood vessels the inflammatory

changes may be studied by cauterising the external surface of any superficial vein (e. g., the external jugular or femoral), or even by simply ligaturing the vessel. Three or four days after the injury the vessel is excised. .The best method is to pass a needle into the knee-joint of a rabbit in such a way that it penetrates into the tibia. A few days after, sections are made of the fresh cartilage and stained in gold. Germination of the

cells of bone may be induced in the long bones of mammalia by passing a red hot needle as deeply as possible into a bone previously freed of the soft parts covering it, and then cauterising the hole with a pointed stick of nitrate of silver, or by violent fracture. After a week or more the bone is excised. Inflammation

of the tissue of the liver may be induced by passing a needle into the organ. Twenty-four to forty-eight hours after the injury the animal must be killed. . The cornea may be cauterised at the centre to such a depth as almost to perforate it, or a thread may be drawn through it, entering at the centre and passing out through the sclerotic beyond the margin, the ends of which are then tied. To study the successive stages of the process, half-a-dozen corneas should be prepared in this way at a time, which can then be excised after eight, twelve, eighteen, twenty-four, thirty-six and forty-eight hours. The best preparations are obtained from rana esculenta during the summer months, from eight to twenty-four hours after the introduction of a silk thread as above described. Inflammation is produced in one eye by cauterisation, and then twenty-four hours after a portion of the cornea of the other eye is excised, spread out carefully, and lodged between the membrana nictitans and the cornea of the injured eye. The membrana nictitans is then drawn up and secured by two or three ligatures to the skin. After twenty-four hours more the sac is opened and the cornea taken out.

The mucous membrane covering the large lymphatic sac of the under surface is snipped off with curved scissors. The observation is necessarily tedious, often lasting for forty-eight hours. It is therefore desirable to replace the tongue in the mouth for a time after each examination. In a curarised tadpole the required

degree of irritation can be produced either by simply pencilling the surface, or by allowing a drop of ammonia to fall on it from a capillary pipette, or, finally, by piercing it with a needle. The research must be continued often for many hours.

Page 166.-Several frogs are then selected, in each of which the pericardium is exposed, and divided as directed in § 46, and a snip made in the ventricle with fine scissors.

Page 174.—In a rabbit two small incisions are made across the course of the external jugular vein (see § 48), one near the clavicle, the other near the origin of the vessel, great care being taken not to go deeper than is necessary, in order to see the vessel through the

fascia. A small needle is then passed under the vein, near the proximal incision, in a direction at right angles to that of its axis, and corresponding to that of the incision, but deeper. A second needle is then laid in the course of the incision, and drawn tightly towards the first by a ligature at either end, by which means the blood-current is entirely arrested, while the coats of the vein are absolutely protected from injury. A second pair of needles is then inserted at the distal incision, and secured in a similar manner so as to shut in the blood with which the vein becomes distended after the tightening of the first ligature. After the lapse of a couple of days the ligatured portion of the vein is exposed at some part of its course, and punctured with a glass pipette, by means of which the blood is withdrawn from it by suction in a perfectly liquid state. The arterial trunks leading from the heart of a frog or tortoise are first tied, and then (as soon as the heart has become distended) the venous trunks. The heart full of blood is removed from the body.

The pericardium of a frog is then exposed and divided, and a snip made in the ventricle with absolutely clean scissors.

Page 176.-A frog having been secured in the usual way (see § 46) in the prone position, the heart is exposed, and the right aorta ligatured. A clip is then placed on the left aorta at its origin from the bulb.

Page 212.-The animal having been secured on Czermak's rabbit board, and the fur clipped, the skin is pinched up between the finger and thumb on either side of the upper end of the trachea so as to form a horizontal fold, which an assistant divides vertically. The opening having been enlarged with the aid of a second pair of blunt forceps, the sterno-mastoid is slightly drawn aside, so as to bring the artery with its three accompanying nerves, the vagus, the depressor, and the sympathetic, into view. The sheath having been opened the artery is raised on a blunt hook, and easily cleared from its attachments to a distance of threequarters of an inch in either direction. When kept closed by the adjusting screw, seize upon the head of a cat or rabbit in such a manner as to hold it firmly without inflicting the slightest injury. The neck of the animal rests on a cylindrical cushion, covered with waterproof cloth, and the rest of the body on a mattress of similar material. Along the edges of the board there are convenient attachments for the extremities.

Page 229.-The excellency of this method lies in the fact that the animal can be kept under observations, without the use of any narcotising drug, for a long time in a perfectly natural condition. The frog is used both in the larval and adult state. To observe the

circulation in the tail of the tadpole, the animal is placed in a moderately strong solution of curare, care being taken to remove it before it is completely paralysed--the moment, in short, that its