274 Mary A. Bowers. 



II. Carmine injection test for leucocytes. 



Renter speaks of the superficial resemblance of the ronnd cells of 

 the epithelium to the round cells of the blood, viz., the leucocytes. 

 Bizzozero ('02) and others have considered them to be leucocytes, 

 but Renter strongly maintains that the two should not be confused, 

 — those of the epithelium arise as epithelial cells and remain epi- 

 thelial cells throughout life. He says that they may migrate to 

 the outer zone of the epithelium and undergo division. 



The round cells of Bufo do not have the appearance of leucocytes, 

 and as they are degenerating cells, it is improbable that they migrate 

 to the distal zone and divide. It was not possible to identify as 

 leucocytes the numerous mitotically dividing cells of the distal zone 

 (Figs. 29-31), in fact none were distinguished in the epithelium. 



To test their presence, and to determine, if possible, whether phago- 

 cytosis plays any part in the histolysis of the epithelium, the method 

 employed by Mercier ('06) in his study of phagocytosis in the tail 

 of Rana temporaria, was tried. Mercier injected powdered sterilized 

 carmine into the dorsal lymph sacs of tadpoles, and the animals were 

 killed 24 hours later. He found that the leucocytes had taken up 

 the carmine granules and wandered with them into the muscular tis- 

 sue of the tail. It was hoped that leucocytes might be traced by this 

 method into the degenerating epithelial tissue of the intestine. 



Tadpoles just ready for metamorphosis were etherized, and ster- 

 ilized powdered carmine was injected under the skin of the back. On 

 the first, second and third days after the injection tadpoles were 

 killed in corrosive-acetic, stained with Delafield's hematoxylin, and 

 imbedded in paraffin. Several series have been carefully examined, 

 with but negative results thus far, no carmine having been found 

 in any of the layers of the intestine. 



III. Contraction of the Intestine. 



Renter and Duesberg refer to the contraction which results in the 

 shortening and narrowing of the intestine as a peristalsis, moving in 

 a cranio-caudal direction. Duesberg states that this peristaltic con- 

 traction is like true peristalsis with the exception that it is permanent. 

 The reduction in size of the intestine, he says, always occurs 



