STRUCTURAL CHANGES IN THE POISON GLAND. 33 



injection and 17 minutes after the last injection of pilocarpine another part 

 was removed. This experiment gave results similar to Experiment IV, the 

 chief difference being the amount of secretion present in the lumen of the 

 tubules. In the present instance this secretion was scanty, whereas in B it 

 was quite abundant. In that part of the gland removed previous to the third 

 injection, the cells containing granules were very few and were found in widely 

 separated parts. In the part removed 17 minutes after the third injection, no 

 granules were seen in any part. 



CONCLUSIONS. 



The experiments with pilocarpine warrant us in drawing the following 

 conclusions : 



(1) Injection of pilocarpine in doses of 0.1 grain begin to act almost imme- 

 diately upon the poison gland, causing within a period of 15 minutes an almost 

 complete disappearance of the secretion granules from the intralobular duct 

 cells. 



(2) Recovery of the gland from the effects of a single injection of pilo- 

 carpine is noticeable as early as one hour after the injection, and is indicated by 

 a swelling of the intralobular duct cells and a formation within them of minute 

 thickenings of the cytoplasmic reticulum. 



(3) Full recovery from the effects of a single injection would appear to 

 require at least an interval of 24 hours. 



(4) Two injections of the usual dosage of pilocarpine, the second injection 

 following the first after an interval of 24 hours, appear to exert a stronger 

 action upon the gland, as after 24 hours' rest a gland so stimulated shows only a 

 partial recovery from the effects of the injection. 



(5) Two injections of pilocarpine, carried out as mentioned in the preced- 

 ing paragraph, appear to have no effect upon the ability of the gland to respond 

 to the action of pilocarpine. A gland injected twice with the usual dose of 

 pilocarpine responded just as readily as a normal gland to the action of the 

 drug after 24 hours' rest, although the gland had only imperfectly recovered 

 from the first two injections of pilocarpine. 



