ON HEREDITY IN NERVOUS DISEASES. 333 



It has been discovered that when a branch of that nervous system 

 is sectioned, is separated from its centre, the blood-vessel with which 

 it is connected almost at once enlarges: its calibre increases, more 

 blood passes through it during a given time, etc. But if, now, this 

 separated end of the nerve is irritated, the reverse phenomena are 

 seen: the blood-vessel contracts, its calibre diminishes. When small 

 arteries are experimented upon, the calibre becomes so small that 

 blood-corpuscles no longer succeed in passing through it. So that it 

 becomes evident that that nervous system has a great function to per- 

 form with regard to the nutrition of all the parts, or rather of every 

 organ in the body, including, of course, the central, i. e., the spino- 

 cerebral nervous system, for the "blood is the life of the anatomical 

 elements." The materials which compose animal bodies are endowed 

 with properties which differ in every different tissue : for instance, we 

 say that the muscular tissue has the property of contracting. These 

 properties of tissues develop functions: for example, the contraction 

 of the ciliary muscle permits correct vision ; but it is evident that if 

 the tissue does not keep up the process of nutrition, i. e., assimilation 

 and disassimilation, which it can only do by the agency of the blood 

 which carries to it new materials, and removes effete elements, its 

 properties are impaired and its functions are consequently perverted. 

 This point being understood, I proceed to relate the experiments : 



If in a Guinea-pig, for instance, that portion of the vaso-motor 

 branch which is in connection with the carotid artery in the neck, 

 which, therefore, regulates the blood-supply of some part of the 

 brain, of the ear, of the face, and of the eye be divided, or, better 

 still, if the ganglion from which that branch springs be removed, we 

 see that the entire half of the head of the animal, on the side on 

 which the operation has been performed, becomes hotter, and on ex- 

 amining more closely we discover that the increase of heat is due to 

 the fact that the blood-vessels allow more blood to pass through them, 

 that the nutrition of the parts is increased, and therefore the heat also 

 increases ; and we see that the upper eyelid of the animal drops a little, 

 being in a state of hypersemia that is, its capillaries are distended 

 that the secretion of tears is increased so that the eye is wet, that the 

 pupil of the eye is contracted because of more blood in the ciliary 

 system, etc. The ear also becomes hotter, and, if the animal is white, 

 we can see that the ear which before was white, with some blood- 

 vessels stretching across, is now become red, and presents a very 

 rich network of capillaries, which have become apparent, being of 

 enlarged calibre. 



Now, all these phenomena may disappear after a while, except a 

 few. The eye always remains smaller, although the blood-supply of 

 the eyelid is more regulated; the pupil remains a little contracted, and 

 the secretion of tears continues, and also the nictitant membrane re- 

 mains in a congested state. No matter how long the animal lives, 



