106 V. E. EMMEL 



latter in contrast to the former does not stain with pyrolblue 

 (p. 45, 49) and the inference consequently arises that the macro- 

 phags of the serous cavities are not derived from the mesothe- 

 lium. Tschaschin ('13, p. 350) not having succeeded in obtain- 

 ing a vital stain for the peritoneal endothelium, also draws a 

 similar conclusion. In experiments with celloidin plates in- 

 serted into the peritoneal cavity, Tschaschin ('13) fm-thermore 

 failed to find that the mesothelial cells manifested any special 

 reaction or potentiality for transformation, but that on the con- 

 trary they quickly disquamated and under the conditions of 

 the experiments took no part in the formation of macrophags 

 (pp. 271, 285, 289). 



Unanimity cannot, therefore, be said to have as yet been at- 

 tained in the solution of the problem. As already indicated 

 with reference to negative evidence, perhaps the strongest data 

 which has been more recently advanced is that derived from such 

 results as that of Goldmann and Tschaschin with vital stains. 

 It remains to be seen what is to be the final evaluation of the 

 data derived from this method. At the present stage of such 

 investigations it may not be without value to note the following 

 points which do not appear to render some of the results so far 

 attained as of a necessarily conclusive character with reference 

 to the question in hand. 



It may be observed that if the reaction of the given tissue 

 (whether endothelial or mesothelial) to the vital stain is nega- 

 tive and that of the macrophags positive, it appears, in some 

 cases at least, that this is taken as evidence that the macrophags 

 could not be derivatives of the tissue in question. But with 

 reference to such a conclusion the question arises as to whether 

 it has been clearly demonstrated, first, that there is such a sharp 

 difference in the reaction of the mesothelium and macrophags 

 and second, that even a material difference in vital stain reac- 

 tion in itself establishes an entire absence of any genetic rela- 

 lationship between the tissues under consideration. In the first 

 place it is not to be overlooked that in some instances at least 

 both mesothelium and macrophags may react alike, for Schule- 

 mann ('12) after injection of Trypanblue in rabbits did not ob- 



