76 HISTOLOGY OF THE POISON-GLANDS OF BUFO AGUA. 



THE PAROTID SECRETION. 



The secretion or venom of these large parotid glands is a thick, milky-looking liquid 

 which leaves a peculiar dirty bluish-green stain on steel with which it comes in contact, 

 viz, on razor-blades used in preparing the glandular material previous to fixation. When 

 dried in the air, the venom forms yellowish scales and we can confirm with enthusiasm the 

 statements of Abel and Macht in regard to the bitterness of the taste of an emulsion of the 

 dried secretion. When ferric chloride is added to a diluted emulsion of the venom the green 

 color of a positive pyrocatechin reaction rapidly appears which turns pink after exposure 

 to the air. Such an emulsion reduces Fehling's solution and gives a red color on treatment 

 with ammonia. 



Microscopically, the venom appears to be a liquid in which many small globules are 

 suspended, floating freely about. They are insoluble in acetic acid, chloroform, and ether. 

 These globules or droplets in the crude venom are usually discrete, but are sometimes 

 crowded together in masses. They are the so-called "poison grains," which all authors 

 who have worked with glands of this type believed to be or to contain the toxic principle 

 of the gland secretion. 



Abel and Macht have described the physiological effects of emulsions of venom and the 

 epinephrin obtained from them on animals, and we do not propose to repeat an account of 

 them here. It is sufficient to say the secretion contains true epinephrin, which is physio- 

 logically, chemically, and polarmetrically identical with that compound obtained in its 

 purest form directly from the adrenal gland. Besides this there is present the digitalis-like 

 bufagin and certain aromatic principles, which give to the venom its characteristic and 

 unpleasant odor. In histological sections of material fixed in formol bichromate, the crude 

 secretion has the yellow color of chromaffin substance. 



Abel and Macht conclude that the secretory function of the glands is under the control 

 of the central nervous system, "as their secretion is discharged in consequence of peripheral 

 irritation of sufficient strength." (Abel and Macht, 1912, p. 324.) 



Seeck (1891) believed that the expulsion of the secretion was the result of the con- 

 traction of the muscles of the skin, but Muhse (1909) has shown definitely that this is not 

 the case, having demonstrated that smooth muscle-fibers do not exist in the skin and 

 that the expulsive act is due to a contraction of the smooth muscle-fibers in the wall of 

 the gland-acinus, and that it occurs in such a way as to force the secretion nearest to the 

 duct to the skin surface first (Muhse, 1909, pp. 344-345). She has noticed also that the 

 secretion is present in the glands in two forms which may be discharged separately on the 

 skin surface. In the outer part of the gland she found a comparatively clear or finely 

 punctate liquid, while in the gland center the secretion was very granular from the presence 

 of coarse globules or "poison grains." Artificial stimulation of the skin, of sufficient 

 strength to cause a discharge of venom, results in the appearance on the skin surface of 

 the clear homogeneous liquid, which is the first of the gland secretion to be ejected. If the 

 stimulation is continued the creamy granular secretion from the center of the poison-gland 

 is expelled and spreads about over the thin fluid first discharged. The flow of creamy 

 secretion continues until the gland-sac is emptied. 



Muhse seems to regard the transparent liquid as a vehicle for the conveyance of the 

 "poison grains" which spread about on the skin surface in the thinner fluid first secreted, 

 believing this dilution of granular fluid would, of course, permit the "poison grains" more 

 easy access to all parts of a hostile oral mucous membrane. W T e will speak further of these 

 two sorts of secretion when describing the poison-gland, since we believe that our work has 



