38 



Scientific Proceedings (31). 



minutes after the submaxillary extract was injected. Question is: 

 Would not this active juice have been secreted even without 

 the efforts to cause a psychic secretion, for the salivary extract in 

 my experience has a latent period in which it produces no very 

 marked secretion ? After that period it may come ; that is, a pro- 

 nounced secretion may come, even thirty minutes after injection 

 of salivary extract and even if there has been no chance for psychic 

 secretion. Pawlow, /. c, p. 70, states that in all cases the latent 

 period after the vagus stimulation of gastric secretion may be from 

 15 minutes to one hour, and even more. 



Hitherto we have known the term " latent period of secretion" 

 only in connection with the stimulation of a nerve going to gland 

 or muscle. We are not so familiar with the use of the term 

 " latent period " in connection with the chemical stimulation of a 

 gland. A moment's reflection will bring the thought nearer to 

 us that even after nerve stimulation, pure and simple, chemical 

 events must transpire in the gland cells which require a certain 

 time for their elaboration. Now, if the stimulation is purely 

 chemical, and not through a nerve, the same or similar chemical 

 events must precede the actual outpouring of secretion. We are 

 still ignorant of the processes that occur during the " latent period," 

 but recent work indicates that they are partially electrical and 

 partially of a chemical nature. We must also consider that the 

 immediate effect of a chemical stimulation, like the immediate 

 effect of a nerve stimulation, may be inhibited. 



There are so many side influences of a physical, nervous and 

 chemical nature which control the phenomenon of the " latent 

 period " that its exact nature and what transpires during it, is still 

 a matter of speculation. 



It may, at first sight, seem paradoxical that the latent period of 

 secretion after sham feeding in dogs is stated by Pawlow to be only 

 5 to 10-15 minutes, and the latent period after vagus stimulation 

 1 5 minutes to one hour — for in both instances the stimulation is 

 transmitted by one and the same nerve to the identical synapses 

 in the gland cells. Pawlow explains this, p. 71, /. c, by his belief 

 that in artificial stimulation of the vagus, the stomach receives the 

 excitatory as well as inhibitive impulses, and the latter check 

 secretion. 



