tion and the opposite motion, the depression of the fang, but we shall only mention the two principal ones. The elevator muscle of the fang is the spheno-pterygoid muscle (a) (see cut 5), which arises along the median ridge of the base of the skull (d) and running backward is inserted upon the enlarged posterior end of the pterygoid bone. The contraction of this muscle pulls direction (1-m-see cut 6) the pterygoids forward, which thus push the lower end of the maxillary forward, the upper end being held in position · by the lachrymal hinge. The tip of the fang describes part of a circle, finally points downward instead of backward. The chief retracting muscle which antagonizes the elevator muscle by acting in the opposite direction is the external pterygoid (ecto-pterygoid muscle b, cut 5) which, arising from the joint between the quadrate bone and the lower jaw, runs forward and is inserted on the outside of the maxillary bone, a little below the joint of the latter, with the outer pterygoid bone. It will be seen that the contraction of this muscle means a pulling backward of the maxillary bone in the direction, p-e (cut 6) resulting in the backward and upward movement of the joint of the fang. The fang itself is a large, very pointed and curved tooth, containing two cavities, the pulp cavity and the poison canal (see cut 7), the former situated on the concave, the latter on the convex side of the tooth." The poison canal has a more or less slit-shaped opening near the base of the anterior side of the fang, and another from the very sharply pointed tip. Between the openings, it is often possible to trace a more or less well defined depressed line. This fang has been evolved from the grooved fang of the opisthoglyph, as the latter has been from the plain tooth of the innocent Ophideans. This structure of the fang may be easily understood by comparing it to a leaf, curling up in dying, the edges meeting and overlapping in the middle, leaving an upper and a lower opening. As to the rapidity of replacement of a destroyed fang, to borrow Dr. Weir Mitchell's words, "When the fang is lost by natural process, it is replaced within a few days, when violently displaced, several weeks sometimes elapse before the next fang is fixed firmly enough to be useful to the snake." If the functional fang be lost or shed, the next tooth gradually as

sumes its position (see cut 9). The poison apparatus outside of the fangs consists of a supermaxillary gland situated on each side of the head, below and behind the eye. A special development occurs in the yellow portion of the venom gland, which poison gland gives to the Crotalid's head a triangular shape. These glands are the homologues of the common parotid. The shape is that of a flattened almond, the pointed end toward the front and below the eye, tapering to a narrow duct which carries the poison to the inlet at the base of the fang. The relative size may be understood by glancing at cut 8. In structure they are racemose glands with elongated acinii. The glandular portion contains columnar epithelium, the ducts pavement epithelium. The blind pouches are lined with the angular nucleated epithelial cells. These cells respond to stimulation, belladonna, for instance. The muscles used in erecting and depressing the fangs have been previously described. In order that the mechanism of the entire poison apparatus may be understood, it will be necessary to briefly name and describe the most important muscles utilized in expressing the secretion of the poison glands. To borrow Stejneger's description, which is brief and explicit, we have "in the non-poisonous snakes the closing of the mouth is effected by the three temporal muscles, the anterior, middle and posterior. The anterior arises from the parietal crest and its continuation of the post-frontal bone turns backward around the joint of the lower jaw to be inserted on the taller bone; the middle arises from the posterior half of the parietal crest, runs downward and forward under the anterior and is similarly inserted, while the posterior, the strongest of them all, arises from the quadrate bone, and is inserted on the inside of the entire length of the angular bone of the lower jaw. In the Crotalids this arrangement is considerably modified (Fig. 8). The posterior (c) and middle (g) temporal muscles remain essentially as in the non-venomous snakes, and their function is also the same, viz., by contraction they pull the lower jaw up against the upper one, or in other words, close the mouth. The anterior temporal (b), however, has now both a different use and function. Instead of connecting with the cranial wall, it arises entire from the upper posterior portion of the firm, tendon

ous capsule of the poison gland (a), runs backward under the ribbonlike ligament (e) which fastens the gland to the joint of the jaw, winds around this joint and inserts itself (b) broadly upon the lower jaw. It may easily be shown that a contraction of these muscles will produce a tremendous pressure upon two-thirds of the poison gland, driving poison out of upper and back part of gland. It is also apparent that this closing of the mouth does not necessarily affect the gland, as only the posterior and middle temporals need be employed in the action, and that the pressure exerted by the anterior temporal is voluntary, as well as independent of the closing of the jaw." During this, the anterior lower angle of gland as well as portion of duct is subjected to similar pressure at same instant by flat tendonous insertion of a part of the external pterygoid upon the jaw. (See cut 8.) At the bend of the poison duct, under the eye, Weir Mitchell has demonstrated a genuine sphincterial muscle which will prevent escape of the precious fluid if needs for months. The secretion of these glands, the so-called venom, has differentiating qualities itself. A pale straw to yellow limpid viscous fluid, with a specific gravity from 1050 to 1065, acid reaction, containing a small quantity of epithelium and a varying amount of solid matter, it bears a marked influence in the prognosis of the bites of the different genera and species. There have been various methods used to obtain this fluid, such as the grasping of the snake behind the head, forcing open the jaws and compressing the glands, thus causing an excretion of the venom into graduates or other containers. The early study of this substance was more one of the proving or disproving of the curative qualities of the various proposed remedies, than as to its constituents. Felix Fontano was one of the first scientists who made any headway, and since his time, 1781, there have been certain points not improved upon. The scientific study of its constituents remained dormant from Fontana's time until Prince Lucien Bonaparte took up the study of the poison secretion of the European viper, in 1843, and, in so doing, made the discovery that it was an albuminous substance, with proteid principles, which he named Echnidene. For nearly twenty years the study of this subject remained as after Bonaparte's exper