420 



SCIENCE. 



[N. S. Vol. XXII. No. 562. 



possible to show that both the phenomena 

 are subserved wholly by the spinal cord, it 

 follows that there are present in the spinal 

 cord various structures, quite distinct from 

 the ordinary motor mechanism, which de- 

 termine the state of inactive tension of the 

 muscles, that is to say, their length while 

 in a state of rest. These tonus-subserving 

 structures are not excited by other poisons, 

 like strychnine, and we have here the fun- 

 damental distinction between strychnine 

 poisoning and poisoning by tetanus toxin. 

 Indeed, it was only by means of the latter 

 poison that 4;he existence of these length- 

 regulating tonus centers in the spinal cord 

 was brought to light. 



I have spoken hitherto of the nervous 

 system itself, but it is true that the physi- 

 ology of structures closely connected with 

 the nervous system, as the glands, heart, 

 blood vessels and muscles, has been ma- 

 terially advanced through the use made of 

 pharmacological agents. You are all aware 

 of the progress in our knowledge of lymph 

 formation and the glandular function, 

 which we owe to studies of Heidenhain; 

 and these again were dependent in a great 

 degree upon the help of pharmacological 

 methods involving the application of spe- 

 cific chemical stimuli. I shall mention the 

 results of some more recent investigations 

 in this same direction, in the belief that 

 they may be less familiar to you. Very 

 recently Wertheimer and Lepage, in Lille, 

 reported a series of pharmacological in- 

 vestigations on secretion by the pancreas, 

 which led them to important results. It 

 has long been known that the pancreas may 

 be stimulated to secretion in a reflex man- 

 ner and also, as Pawlow showed, through 

 direct irritation of the vagus nerve. We 

 know also, as a result of Starling's work, 

 that the pancreas can be thrown into ac- 

 tivity directly through the specific chemical 

 stimulus furnished by the presence of se- 

 cretion in the circulating blood. Now, 



Wertheimer and Lepage were able to show 

 that the gland has at least two distinct 

 mechanisms through which it is possible to 

 excite the secretion of pancreatic fluids; 

 first, certain structures intimately con- 

 nected with the vagus nerve, which may 

 be excited by pilocarpine, physostigmine 

 or muscarine, or completely paralyzed by 

 atropine ; and secondly, another set of 

 structures which are not acted upon by 

 these poisons, being neither excited nor 

 paralyzed by them, but which react to cer- 

 tain other definite chemical stimuli like 

 secretin. Possibly the latter apparatus is 

 part of the sympathetic nervous system; 

 at all events the case of the submaxillary 

 gland has been brought forward by Wer- 

 theimer and Lepage as analogous, since in 

 this case the terminations of the chorda 

 may be influenced by pilocarpine and 

 atropine, whereas the sympathetic nervous 

 mechanism remains intact. And, finally, 

 just as the salivary secretion differs accord- 

 ing as it arises through the stimulation of 

 the chorda or of the sympathetic nervous 

 system, so does the pancreatic secretion 

 resulting from the pilocarpine differ from 

 that which is obtained through the action 

 of secretin. In the latter case the secretion 

 contains entero-kinase, that is to say, is 

 able to digest albumin without the addition 

 of succus entericus. 



In this connection it may be mentioned 

 that the use of pilocarpine has led to a 

 physiological understanding of an entirely 

 different kind of secretion, namely, the 

 liberation of a gas. It has long been known 

 that the swimming bladder of fishes con- 

 tains a gas, the presence of which can 

 hardly be explained by a process of simple 

 diffusion out of the tissues. This fact, 

 which we owe to the observation of Huef- 

 ner, led Dreser to investigate the process of 

 liberation of oxygen into the swimming 

 bladder of the pike, with a view to de- 

 termining whether pilocarpine and other 



