16 PRINCIPLES OF VETERINARY SURGERY 



well as the organ itself. In man, the upper part of the duo- 

 dejium has been trained to do the work of the stomach, and 

 even one hemisphere of the brain can be removed, and the 

 other made to take its place. Almost the entire thyroid gland 

 can be taken out and the remaining part will perform the 

 physiological duties of the whole organ. If one ovary or tes- 

 ticle be removed, it will not interfere with the generative 

 functions of the animal. The bladder can be dispensed with 

 by transplanting the ureters into the intestines ; the lower 

 bowel, by attaching the remaining portion of intestines to the 

 external abdominal wall ; the oesophagus, by inserting a tube 

 into the stomach ; and furthermore, the various organs have 

 been transplanted from one animal to another, such as the 

 ovary, kidney, thyroid gland, etc. This is still in the ex- 

 perimental stage. 



In pathological regeneration, the new tissue is formed by 

 the proliferation of cells in the immediate neighborhood of 

 the area from which the cells have been cast off or destroyed. 

 The new tissue is d.erived from tissue of like kind ; epithelium 

 from epithelium, muscle from muscle and connective tissue 

 from connective tissue. There are two methods of reproduc- 

 ing cells, — direct division or amitosis, and indirect division 

 or karyokinesis. In amitosis, the mother-cell simply in- 

 creases in size and finally divides directly into two daughter- 

 cells after a division of the nucleus. In karyokinesis, the 

 process is more complicated, consisting in a cycle of definite 

 changes involving first the nucleus and then the cell-body. 

 The latter mode of division is the most common. 



The faculty of reproduction is not possessed by all the tis- 

 sues in the same degree. Ganglion-cells are rarely reproduced, 

 if at all, in the adult, and many glandular epithelial cells have 

 a limited power of reproducing themselves; whereas the 

 surface epithelium, the epithelial cells in the lining of ducts 

 and particularly the connective-tissue cells, have great power 



