136 CARL R. MOORE 



recovering from the anaesthetic. The rats were so marked and 

 caged that individual animals could be recognized at all times. 

 At the desired time the animals were killed, the grafts removed 

 from their positions, as was also the normal intact gonad, and 

 the tissue preserved in Bouin's fluid. Paraffin sections were 

 prepared and stained with Delafield's hematoxylin and eosin. 



There were a considerable number of cases in which the grafts 

 did not persist, as well as a small number of deaths of animals 

 before a study of the glands could be made; however, positive 

 persistence of grafts was obtained in over 50 per cent of the cases. 



Operations of the same character as those described above 

 have been carried out on guinea-pigs instead of rats; these have 

 not been of any considerable number, and all results have so far 

 been negative. Experience has shown, however, that grafts 

 grow more readily in rats than in guinea-pigs, and no especial 

 significance has been attached to the non-persistence in cases 

 where a sex gland of the opposite kind from the graft was intact 

 in the host. 



Due to the fact that many pieces of tissue of large size were 

 taken from the rats at the time of killing and that one is not 

 certain of the character of the tissue so taken until after section- 

 ing and staining, all tissue was preserved in the same way, cut 

 at the same thickness, and stained with the same stains. So 

 far the writer has made no attempt to stain differentially the 

 interstitial cells of these grafts; many times the material is 

 decidedly unfavorable for such staining, as the tissue, especially 

 the testis, may be considerably infiltrated with connective tissue 

 which had invaded it during growth. The interstitial cells of 

 the rat testis are, moreover, relatively small, and possess little 

 specifically characteristic. The present paper will deal with 

 considerations of the gland tissue in general rather than with the 

 interstitial cells as specific tissue. 



