TRANSPLANTATIONS 41 



animals there are typical homoiogenous reactions, occasionally reactions ap- 

 pear which are more characteristic of syngenesiotransplants, and even as late 

 as 20 to 25 days following transplantation the grade 3— was obtained in a 

 younger host, which signifies that the structure of the graft approached that 

 seen after autotransplantation. In older guinea pigs the reactions were more 

 severe. However, we found that in different series of experiments with guinea 

 pigs obtained from different breeders, the severity of the reactions differed 

 somewhat, in the same way as in transplantations in the rat. 



The grades obtained between 20 and 25 days after homoiotransplantation 

 were 1,1 + , and 2—. Between 25 and 40 days, in the majority of cases, the 

 grade was 1 ; in only one-third of the cases the grade 1+ (1.25), and in no 

 case grade 2— (1.75), was reached. In younger guinea pigs the grades be- 

 tween 20 and 25 days were somewhat better; they varied between 1 and 2, 

 and even grade 3 — (2.75) was attained. Even after 50 and 60 days, while 

 the grade was mostly 1, in a few cases grades 2— /1+ (1.50), or even 

 2/2— (1.87), were obtained. 



3. The effect of feeding thyroid substance to guinea pigs which are hosts of 

 thyroid transplants. If preparations of thyroid gland are added to the diet 

 of normal guinea pigs, the mitotic activity of these transplants decreases and 

 the colloid becomes hard, as an indication of the diminished function of this 

 gland. However, when we gave, by mouth, daily 0.1 grain of thyroid to 

 guinea pigs which received autotransplants of thyroid gland, the success of 

 the transplantation was not diminished thereby, although the height of the 

 acinar epithelium was low or medium to low. No increase in connective tissue 

 nor in lymphocytes took place. Likewise, in guinea pigs with homoiotrans- 

 plants of thyroid gland, thyroid feeding did not have any noticeable effect 

 on the reaction of the host against the transplant. The grade in one guinea 

 pig, after 30 days, was 1 ; after 20 days, the grades were : 1 in 6 guinea pigs ; 

 2— in 2 guinea pigs ; 2 in 3 guinea pigs, and in 2 additional guinea pigs it was 

 2 and 2— respectively. After 13 days, the grade was 1 — . In a second experi- 

 ment with younger guinea pigs the grades varied between 1 and 2. The effect 

 which administration of thyroid hormone exerts on the thyroid gland did 

 not, therefore, change the reaction of the host against transplants of this organ. 



Autogenous and homoiogenous transplantation of cartilage and fat tissue 

 in rat and guinea pig. 



4. Autotrans planted xiphoid cartilage in the rat, as a rule, remains well 

 preserved and the perichondrium is free of lymphocytes, in rat (as well 

 as in guinea pig) only when the cartilage has been injured as the result of 

 the operation, or is poorly nourished, owing to pressure or hemorrhage in 

 the surrounding tissue or other injurious factors, it becomes necrotic. Thus, 

 if the thick end of the cartilage near the bone is transplanted, the center of the 

 transplanted piece may be at a disadvantage because of the lack of nourishment 

 and may become necrotic and dissolved ; subsequently, connective tissue may 

 invade and replace the necrotic central areas. Necrotic pieces of cartilage may 

 be surrounded by connective tissue which has grown into and replaced the 

 transplanted fat tissue, or the perichondria! tissue may produce a new plate 



