60 PRINCIPLES OF STOCK-BREEDING. 



" If in a Guinea-pig, for instance," says Dr. Dupuy, 

 "that portion of the vaso-motor branch (of nerves) 

 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, be- 

 comes hotter, and, on examining more closely, we dis- 

 cover 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 dis- 

 tended that the secretion of tears is increased, so 

 that the eye is wet, that the pupil of the eye is con- 

 tracted, 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 be- 

 come red, and presents a 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, al- 

 though the blood-supply of the eyelid is more regu- 

 lated ; the pupil remains a little contracted and the 

 secretion of tears continues, and also the nictitant 

 membrane remains in a congested state. No matter 

 how long the animal lives, that state of the eye per- 



