The rôle of phagocytosis in involuting organs

Abstract

In order to clear the way for a study of the transfer of protein in the involuting tail of the tadpole, it was necessary to reëxamine the rôle which has been ascribed by Metschnikoff, Barfurth, Bataillon, Mercier and many others to the leucocytes in producing the phenomenon. Looss believes on histological ground, that if leucocytes play any part in the process of tissue atrophy and absorption, they play a minor and secondary one rather than a primary rôle. The process of atrophy begins prior to the invasion of the leucocytes into the muscle of the tail and this has been described by Mercier and others, who hold that phagocytosis is the principal factor. Moreover, it has been described for other involuting organs, such as in the metamorphosis of insects, the absorption of the gills of amphibia, etc. It has been suggested for the involution of the mammalian uterus, likewise, so that it may be said that investigators are in accord in observing a dissolution of the muscles and other tissues in atrophying organs prior to the advent of leucocytes.

It is to be expected that if phagocytosis plays any important rôle in the inception of the process of absorption of tissue in the larva of the frog, the blood would show an increase in the total number of leucocytes during the stages of metamorphosis and moreover there would be an increase in polymorphonuclear leucocytes during these stages, to compensate for the drainage of these cells into the muscles. In order to examine this point, smears were made of the blood from the larvz of the bull-frog, Rana catesbiana and from the western pickerel frog, Rana areolata. Thirty specimens were used, the blood being permitted to flow into a capillary tube from a lesion in the heart and then blown upon a slide, dried in the air and stained with Wright's stain.