Transplantation. 251 



fatal complications do not develop such lesions do not end in 

 new formation of nervous elements but in fibroplastic cicatrization. 



Regeneration of Blood Corpuscles and Lymph Cells. — The resto- 

 ration of blood cells does not take place within the blood vessels, but 

 originates in those organs in which normally the continual replace- 

 ment of worn out cells of the blood and lymph is accomplished, par- 

 ticularly the bone marrow, spleen, lymph nodes and in lymphoid 

 germinal foci scattered about in various tissues. The red blood 

 corpuscles develop entirely from cells of the medulla of bones and 

 are nucleated when first formed ; b}' the time they have entered the 

 circulation their nuclei have disappeared. Serious or repeated loss 

 of blood cells calls forth so marked a proliferation of the hemo- 

 poietic marrow tissue that the fatty marrow of the long bones comes 

 to resume its embryonic character and is changed into red marrow. 

 The colorless corpuscles are produced by proliferation of the leuco- 

 cvtes and Ivmphocvtes in the structures mentioned and pass out into 

 tlie blood. 



The fluid portion of the blood is renewed by the passage of 

 water and salts from the tissues into the lymph and blood capilla- 

 ries. 



Transplantation. 



Some cells and tissues can maintain their vitality for some time 

 after their removal from the animal body and are capable of renew- 

 ing their growth if artificially implanted upon another part of the 

 same body or in another animal.* Experiments in transplanation 

 have been performed frequently and sometimes successfully by 

 surgeons ever since the fifteenth century, for the purpose of re- 

 storing denuded parts of the skin and other tissues in man ; and, 

 too. the same experiments have been repeatedly performed in ani- 

 mals in order to obtain theoretical grounds for operative procedures 

 and explanations of pathological questions. 



It is most easilv and successfully performed in lower animals. 

 Born has succeeded in causing adhesive growth in pieces cut rflf 

 from larval amphibians to take place in various ways, as of the 

 head end of one larva to the tail end of another. Joest succeeded 

 in uniting the opposite ends of earthworms. As interesting trifles, 

 after the castration of cocks the spurs used to be often cut off and 



* Inoreranic particles, as bits of ivory, wire or bullets, if they get into or 

 are introduoed into the tissues (implantation. Insertion) may be encapsulated, 

 that is. surrounded bv connective tissue. Even living- or dead tissues may 

 be similarly surrounded, as an extracted tooth may be thus held in an alveolus 

 in which it is implanted. In transplantation, also known as grafting (French, 

 <i>Tffe). there is not merely an encapsulation or adherence of the tissue 

 to the' structure, but in addition it multiplies in the site of Implantation and 

 forms part of the organic structure with the tissue about it. 



