262 STUDIES IN ADVANCED PHYSIOLOGY. 



There is, therefore, no difficulty in interpreting these 

 phenomena. To restate it, it is this. The gland cells re- 

 ceive two kinds of nerves. First, those from the cerebro- 

 spinal system, which when stimulated cause the transuda- 

 tions to wash the specific elements out of the glands. 

 Secondly, the sympathetic nerves which control the pro- 

 duction of the specific elements themselves. The sympa- 

 thetic nerve is no doubt more or less in action all the time, 

 and in this way the gland is busy in the production of the 

 specific elements in the periods of apparent rest when there 

 is no secretion flowing from the gland, while the cerebro- 

 spinal nerve is called into play at the moment the secretion 

 is wanted, and brings" about a copious flow of water and 

 mineral salts through the gland, by means of which these 

 specific elements are carried out. Of course just at this 

 time the stored antecedent granules in the various glands 

 are finally changed into the regular specific elements; 

 otherwise the transudations would not be able to carry them 

 out. For instance, in the pancreas the trypsinogen granules 

 would not be affected by the water and salt secreted, but it 

 would at that point change into the soluble trypsin which is 

 readily washed out. 



It was pointed out before that along with the stimula- 

 tion of the cerebro-spinal nerve there is a stimulation of the 

 vaso-dilator nerves going to the arteries of the glands, so 

 that while the transudations are being poured Out of the 

 gland the gland itself seems flushed with the distended 

 arteries. From the foregoing it is evident that the gland is 

 not exerting itself most at the time the secretion is actively 

 pouring out, but that the real constructive period of activity 

 is the one between such times of flow, the period during 

 which the specific element is gradually built and stored up. 

 It was pointed out that the cerebro-spinal nerve seems 

 wholly concerned with the water and the salt transudations, 

 and the sympathetic nerve wholly with the production of 

 the specific elements. While this is in the main true, there 

 are physiologists who believe that the cerebro-spinal nerve 



