TRANSPLANTATION OF TISSUES. 497 



When this is the case, the part becomes inflamed and swollen, owing to an 

 exudation of plasma. The blood-vessels become dilated and congested, and, 

 notwithstanding the slower circulation, the amount of blood is greater. The 

 blood-vessels are increased, owing to the formation of new ones. Colourless blood- 

 corpuscles pass out of the vessels and reproduce themselves, and many of them 

 undergo fatty degeneration, whilst others take up nutriment and become con- 

 verted into large uninucleated protoplasma-cells, from which giant-cells are 

 developed (Ziegler, Cohnheim). The newly-formed blood-vessels supply all these 

 elements with blood. 



245. Transplantation of Tissues, 



The nose, ear, and even a finger, after having been severed from the body by 

 a clean cut, have, under certain circumstances, become united to the part from 

 which they were removed. 



The skin is frequently transplanted by surgeons, as, for example, to form a new 

 nose. The piece of skin is cut from the forehead or arm, to which it is left 

 attached by a bridge of skin. The skin is then stitched to the part which it is desired 

 to cover in, and when it has become attached in its new situation, the bridge of 

 skin is severed. 



Reverdin cut a piece of skin into pieces about the size of a pea and fixed them 

 on an ulcerated surface, where they, as it were, took root, grew, and sent off from 

 their margins epithelial out-growths, so that ultimately the whole surface was 

 covered with epithelium. 



The excised spur of a cock was transplanted and fixed in the comb of the same 

 animal where it grew (John Hunter). 



P. Bert cut off the tail and legs of rats and transplanted them under the skin of 

 the back of other rats, where they united with the adjoining parts. 



Oilier found that, when periosteum was transplanted it grew and reproduced 

 bone in its new situation. Even blood and lymph may be transfused (Trans- 

 fusion p. 199). 



All these results seem only to be possible between individuals of the same 

 species, although Helferich has recently found that a piece of a dog's muscle, when 

 substituted for human muscle, united to the adjoining muscle and became 

 functionally active. [While J. R. Wolfe has transplanted the conjunctiva of the 

 rabbit to the human eye]. Most tissues, however, do not admit of transplanta- 

 tion, e.g., glands and the sense-organs. They may be removed to other parts of 

 the body, or into the peritoneal cavity, without exciting any inflammatory 

 reaction ; they, in fact, behave like inert foreign matter. 



246. Increase in Size and Weight during Growth, 



The length of the body, which at birth is usually ^ of the adult body, undergoes 

 the greatest elongation at an early period : in the first year, 20; in the second, 10; 

 in the third, about 7 centimetres; whilst from 5-16 years the annual increase is 

 about 5| centimetres. In the twentieth year the increase is very slight. From 

 50 onwards the size of the body diminishes, owing to the intervertebral discs 

 becoming thinner, and the loss may be 6-7 centimetres about the eightieth year. 

 The weight of the body (^ of an adult) sinks during the first 5-7 days, owing to 

 the evacuation of the meconium and the small amount of food which is taken at 

 first. 



The increase of weight is greater in the same time than the increase in length. 

 Within the first year a child trebles its weight. The greatest weight is usually 



32 



