ioo Animal Morphology. 



The par vagum, or hcemal sense, is supposed to give conscious- 

 ness to its owner both of hunger and suffocation, etc., according 

 to the state of the blood in that particular organ to which it 

 is distributed, in contrast to those senses which give 

 consciousness to pressure, resistance, and external stimuli. 

 Hence, in determining the function of this sense by 

 irritants and mechanical injuries, only one side of the 

 question is settled, and that is the negative one, or the 

 want of action ; nay, even the par vagum may be cut, and 

 the cut end of the nerve on the proximal side to the brain 

 may give sensation to the central mass as though it were 

 still intact, and acts may follow as if it were in its natural 

 condition, so far as eating and breathing are concerned. Just 

 as men with an amputated leg often speak of the toes 

 itching or the limb paining, which no longer exists as an 

 integral part of the body, so after section of the par vagum 

 acts follow from mere sight, which are dictated by central 

 sensation. Certain states of blood, as of given conditions of 

 acid as of carbonic, lactic, hydrochloric, etc., etc., which has 

 not yet been fully excreted from the capillary network are 

 supposed to be the natural stimulants to the par vagum in 

 exciting the feeling of hunger and suffocation, etc., the one 

 pertaining to the lungs, the other to the stomach. No 

 doubt the heart, liver, and small bowels yield certain morbid 

 feelings when their functions are impaired from some altered 

 condition in the capillary system of the organ affected. 



The par vagum, then, is considered to be a true sense,, 

 placed in proximity and juxtaposition with the other senses 

 in the great central mass the brain. 



This sense gives information to the brain of certain wants 

 and states belonging to the organic, or vegetative conditions 

 of the body, more especially that of the stomach and lungs, 

 but leaves to other senses information beyond this part of 

 bodily framework. 



