378 SERGIUS MORGULIS 



Savitch, A. A. — New Materials for the Study of the Influence of Nutritive Reflexes 

 Upon Each Other. 



The influence of various substances used as nutriment is studied by the method 

 of conditioned reflexes, the organism being either surfeited with or deprived of the 

 particular substance. Meat powder, granulated sugar and cracker meal are used. 

 Two dogs were deprived of meat, being abundantly fed on sugar. The conditioned 

 reflex worked out for the meat powder diminishes very much at first showing thus an 

 intense excitation of the sugar subcentre and an inhibition of the meat subcentre. 

 The overexcitation of the sugar subcentre results, however, in fatigue, whereupon 

 the meat conditioned reflexes increase again. It must, therefore, be considered as 

 proven that food stuffs exert an influence in the direction of inhibition conditioned 

 reflexes established to other food stuffs. But the influence depends upon the organic 

 need of the animal for one or another nutritive constituent, or, in subjective terms, 

 upon its taste. An increased need of the animal of food constituents of which it 

 has been deprived lasts a variable time depending upon the length of privation, and 

 can be easily detected by the degree of conditioned salivary response. The physio- 

 logical reaction produced by the food materials on the lining of the mouth and on the 

 taste and organs are discerned by the mouth analyser exactly as sound stimuli of 

 different frequency of vibration are discerned by the auditory analyser. 



Jerofeeva, M. N. — Electrical Irritation of the Skin of the Dog as a Conditioned 

 Stimulus of Secretion of the Salivary Glands. 



The irritation caused by a sharp instrument inhibits both the natural and artificial 

 conditioned salivary reflexes. The degree of inhibition depends upon the strength 

 of the irritation. The inhibition caused by irritation with the sharp instrument 

 gradually decreases, i. e., this irritation represents a waning inhibitor. A weak 

 faradic current has a similar effect and may become the conditioned stimulus of 

 secretion. The faradic current of such slight strength may, however, cause also a 

 sleeping reflex. The sleepy state induced by the electric current is not as deep as 

 when produced by a thermal stimulus. The sleeping reflex occasioned by the elec- 

 trical stimulation is accompanied by salivary secretion in response to various irrele- 

 vant factors. During sleep the conditioned reflex to the electrical irritation as well 

 as to stimulation of other analysis disappears. The sleeping reflex may be counter- 

 acted by intermissions in the experiment, by change of strength of current or by 

 change of place of stimulation. This sleeping reflex interferes with the development 

 of differentiation as to the locality of the skin. The conditioned reflex obtained 

 with a faradic current applied to different regions of the body varies in intensity 

 according to the sensitiveness of the skin in the particular region. The least sen- 

 sitive part of the skin is that directly above spinal column and on top of head. The 

 most sensitive part is on the inner surface of hind legs, on the intercostal spaces and 

 tail. 



The irritation of the skin with a very strong faradic current forms a conditioned 

 salivary reflex. As the irritation grows the reflex also increases. The defensive 

 reflex at first called forth by the electrical stimulation is lost when the conditioned 

 salivary reflex appears. Even before the salivary reflex has been fully formed the 

 process of eating soothes the violent defensive reflex. Neither in the case of the strong 

 nor of the weak faradic current can a conditioned salivary reflex develop with regard 

 to acid. 0.25% of HC1, when poured into the mouth apparently blocks the con- 

 ditioned salivary reflex to electrical stimulation, while it may increase the reflex to 



