GENERAL PROPERTIES AND ACTIONS OF THE VENOM. 53 



INFLUENCE OF PILOCARPINE ON THE SECRETION OF VENOM. 



In order to obtain greater quantities of venom we injected subcutaneously 

 0.1 grain of pilocarpine into a heloderma from which all secretion obtainable by 

 the usual method had been collected. As a rule, in from 1 to 3 minutes after 

 the injection the flow began again and lasted now 20 to 30 minutes, reaching 

 its maximum at 10 to 15 minutes after injection of pilocarpine. The flow 

 induced by pilocarpine not only lasts longer, but is more abundant than the 

 ordinary flow and frequently reaches three or four times the amount obtained 

 without pilocarpine. However, the influence of pilocarpine can not be main- 

 tained permanently. By its use venom may be obtained from an animal 

 that has just previously yielded none, but if such an animal be injected with 

 pilocarpine on the succeeding day no secretion will be obtained in consequence. 

 We found that in animals yielding venom freely the first injection of pilocar- 

 pine caused increased secretion; the second injection (on the succeeding day) 

 caused a secretion where none was previously to be obtained; the third injec- 

 tion was without result. In those animals which secreted venom freely the 

 first injection of pilocarpine caused an increase in the secretion of venom; when 

 the second injection of pilocarpine was given on the day following the first 

 injection, the venom glands were again stimulated to secretion of venom, 

 although before the injection of pilocarpine it had been impossible at this time 

 to collect any venom; when a third injection of pilocarpine was given to such 

 an animal on the day following the second injection, no venom was secreted.* 

 This failure of the venom glands to respond to the third injection of pilocarpine 

 is probably due to exhaustion of the secreting-cells, an exhaustion from which 

 the cells are unable to recover in so short a period of time as 24 hours.f As a 

 rule, the first injection causes also discharge of urine and feces, whereas suc- 

 ceeding injections do not have this effect. The variations in the reaction of 

 the Heloderma to succeeding injections of venom are perhaps partly to be 

 explained by the fact that the animals were fed but once or twice a week. 

 After the first two doses of pilocarpine have set up a genuine secretion of the 

 venom, a new formation of the venom takes place only very insufficiently, and 

 a third dose of pilocarpine is therefore without much effect. After a third 

 injection the gland-cells still secrete the very small amount of venom stored up 

 within the cells. Whether the pilocarpine, besides causing a real secretion of 

 the venom, also causes a discharge of venom already secreted, we can not state. 



Twenty-one helodermas in all were investigated with reference to the 

 influence of pilocarpine upon the amount of secretion. In every case the first 

 dose brought about increase of secretion. The second dose also produced 

 increased flow when the animal had been previously yielding well, and only at 

 the third dose was there no increase. Three animals were subjected to more 

 than three successive injections and all of these died. Sixty animals most 



*In one case an animal which had responded to a first injection of venom did not give an increased amount of 

 venom under the influence of a second injection of pilocarpine given 40 hours later. 



tThese observations on the functional effect of pilocarpine are in good agreement with the observations con- 

 cerning the effect of pilocarpine on the morphology of the venom gland recorded in the paper by Fox and Loeb. 



