THE VAGUS A TRUE SECRETORY NERVE. 53 



In all instances when the pieces of meat were administered at 

 intervals, the quantities of juice were much smaller than when the 

 animal was continuously fed. 



From the above data it follows, first, that specific secretory 

 fibres, and not merely vaso-motor, run in the vagus to the gastric 

 glands; and, secondly, that one must divide these fibres, as Heidenhain 

 did for the salivary glands, into true secretory and trophic. This is 

 shown by the fact that the separation of the water and the preparation 

 of the solid constituents obviously take place independently of each 

 other. We have already seen a number of instances in the second 

 lecture where similar hourly quantities of juice were secreted with 

 wholly different amounts of ferment, dependent on the working con- 

 ditions of the glands. 



But while the nerve-section experiment speaks eloquently in favour 

 of the existence of secretory nerves to the stomach, it is nevertheless 

 desirable, for many reasons, to take into consideration the excitation 

 method also. It is only by artificial excitation that we can study accurately 

 and in all its features the mode of working of a given nerve and the 

 process which it controls. In certain cases great difficulties come 

 in the way of the experiment. This accounts for the failure of 

 the many authors who have previously worked at the question. In 

 carrying out the investigation we have had once more to resort to a 

 special arrangement of our own. We started with the assumption that it 

 is very doubtful if the ordinary so-called " acute " experiment, performed 

 at one sitting on a fresh unprepared animal, can be accepted as a true 

 interpretation of normal conditions in the organism. In such experi- 

 ments many physiological phenomena are misrepresented or, indeed, 

 wholly masked. In our case this doubt was all the more justified 

 because unquestioned proof of the inhibitory effects of sensory and 

 reflex stimuli in general, upon the activity of the most important 

 digestive glands had already been recorded in the literature. It was 

 shown by Bernstein,* in Ludwig's laboratory, and later by myself, in 

 conjunction with Professor Afanassjew,* that sensory stimuli frequently 

 and unquestionably inhibit the work of the pancreatic gland for long 

 periods of time. Dr. Netschajew t has found also that an excitation of 

 the sciatic nerve for two or three minutes is able to bring gastric 

 digestion for several hours to a standstill. From this arose the attempt 

 to excite the nerves passing to the stomach in such a way that no 

 sensory or other reflex impulses could precede or accompany the 

 experimental stimulation. 



* Pfliiger's Archir. Bd. xvi. 



f Vber kemmpndc El nfl iixw anf il'ic Absondemng dm Mniii-it.-ml'tfx. Fnaug-Diss. 

 St. Petersburg, 1882. 



