432 VERA DANCHAKOFF 



An attempt was made by IVIurphy"' ^-' i^. ^ to furnish experi- 

 mental proof of the significance of the small lymphocytes as 

 factors of natural and induced immunity. On the basis of 

 Murphy's work, Jacques Loeb^" has suggested that the greater 

 tolerance of plants to grafts of foreign tissue, as compared to 

 animals, may be explained by the absence of 'leucocytes.' 

 Recent work by Bullock,^ Stevenson,^*. 24 Sittenfield,2o. 21, 22 and 

 Wood and Prime,^^ however, indicate that the role of the small 

 lymphocytes in resistance is more than dubious. Further 

 attempts to establish a causal connection between immunity and 

 the* presence of 'leucocytes' in general seem, therefore, to be 

 unwarranted. 



The mechanism of the resistance attributed to the action of 

 the spleen as a whole or to that of the small lymphocytes has not 

 been discussed, and little, if anything, is known concerning the 

 reason for the failure of a tumor to grow in an immune animal. 

 It is true that a detailed morphological study by RusselP^ and 

 Woglom^^ of the conditions at the site of a graft which has 

 failed to develop has revealed a lack of a stroma reaction in the 

 immune host and a failure of vessels to grow into the grafted 

 tissue which resulted in the subsequent necrosis of the graft. 

 This observation, important as it is, gives no further informa- 

 tion concerning the nature of the resistance; the reason why 

 the vessels do not grow into the grafted material in an immune 

 animal remains unexplained. 



The purpose of the present paper is to show that the phago- 

 cytic and digestive capacity of the mesenchymal syncytium or 

 cellular reticulum of the adult chicken spleen is a direct and 

 decisive factor in the destruction of the Ehrlich mouse sarcoma, 

 and a factor of partial inhibition to the Crocker Fuiid mouse 

 sarcoma 180, both of which grow vigorously when grafted alone 

 upon the allantois of the chick embryo. The mechanism of this 

 inhibition is easily demonstrable and will be described in detail. 

 I am far from being able to extend my results to other tumors. 

 On the contrary, numerous indications point to the fact that the 

 capacity of the splenic mesenchyme to destroy living tumor cells, 

 as described in this paper, is due to the association of very defi- 



