1USTOI.OCY OK TIIK l'OISO\-(, LANDS OK Ml'Ko Adl'A. 83 



squirted out for sonic distance. If, for example, I lie gland* are squee/ed with large hysteivr 

 touiy forceps, the venom will spurt out and cling to the sides of a glass bowl held over llie 

 animal, where it may be collected. Wehavenot seen such spurt ing under mechanical stimuli, 

 but Budget t states that if the toad he roughly handled, the parotids discharge like squirts. 



Muhse has noted that the first discharge on stimulation is the clear homogeneous 

 liquid from the outer parts of the gland acini. If the stimulus is continued, the clear liquid 

 is followed by the typical milky secretion of the gland which flows about in the clear fluid 

 and ultimately mixes with it. She believes this clear liquid to be a sort of vehicle which 

 dilutes the more viscid fluid containing the poison grains and so permits the free diffusion 

 and spread of the venom on the surfaces with which it comes in contact. In common \\ it h 

 most authors, she evidently believes the poisonous principle of the venom to reside in t In- 

 so-called poison grains, of which she says: "The granules of the mature secretion are 

 known to have an irritating or poisonous effect on the mucous membranes of other animals." 

 This may be the case, since we are not prepared to say whereabouts in the venom the second 

 poisonous principle, bufagin, is found, but the chromamn reaction shows very clearly that 

 the first response of the toad to stimulation is the excretion, not of a mere diluent, but a 

 strong solution of the most powerful poison at his command. This is what one would 

 expect, since logically it is to the toad's advantage to eject the substance which will produce 

 the most severe ami immediate discomfort to his enemy. 



When a gland has discharged its secretion it does not refill, but is replaced by a new 

 one. Where does the new gland originate? Young poison-glands may, we believe, grow 

 down directly from the epidermis, beginning, as do the ordinary mucous skin glands, as an 

 epithelial bud from the stratum germinativum and pushing downward into the cutis, but 

 this is not the common means of glandular regeneration. 



Bristol and Bartelmez we have already quoted on the subject: ''When the poison is 

 discharged, the remains of the glands are resorbed, and at the same time one of the five or 

 six undeveloped glands grouped around the mouth of the functioning gland grows down 

 alongside the remains of the discharged gland, pushing it aside to occupy its former place." 

 This is in brief exactly what occurs. The ducts of these huge parotid poison-glands are 

 branched a short distance below the epidermal foveolae, smaller ducts leading off in an 

 irregular ring radially and downward from the neck of the functioning gland, to which they 

 have the same relation as the ribs to the rod of an umbrella. Each branch terminates in a 

 young, developing poison-gland. Different stages of gland development maybe observed 

 in the group of young glands surrounding a single functioning one. 



The shape of the immature glands is round or oval generally, but glands may be aeen 

 which are lobated or which are flattened on one side, and the young glands lie at different 

 depths in the corial strata. We have not had an opportunity of studying embryonic mate- 

 rial, but it would seem probable, from some of our adult specimens, that the glands of this 

 type arise by downward budding from the epidermal stratum germinativum, in the same 

 manner as do the ordinary small mucous glands of the skin. As a gland grows down into 

 the depths of the corium other young glands bud from the stratum germinativum of the 

 gland-duct or from the epidernus in its immediate vicinity (fig. l'. so I hat a small group of 

 young glands is found in the corium about a central one or parent. Only one of such a 

 group functions at a time. The gland carries with it, down into the corium, the outer loose 

 layer of the connective tissue which around the acinus enlarges proportionately with the 

 acinar growth and becomes the wide layer of loose connective tissue immediately surround- 

 ing the adult gland. In this downward course the corial melanophores are also dragged 



