author's abstract of this paper ISSUEL 

 BY THE BIBLIOGRAPHIC SERVICE, NOVEMBER 15 



THE DEVELOPMENT OF THE MAMMALIAN SPLEEN, 



WITH SPECIAL REFERENCE TO ITS 



HEMATOPOIETIC ACTIVITY 



GEO. A. THIEL and HAL DOWNEY p 



Hematological Laboratory, Department of Animal Biology, University of Minnesota 



THREE TEXT FIGURES AND THREE PLATES (EIGHT FIGURES) 



INTRODUCTION 



To anyone looking over the literature on the development of 

 the mammalian spleen the necessity for more work on the finer 

 details of the process is evident. In spite of an extensive litera- 

 ture, one finds few recent papers dealing with the subject from 

 the standpoint of the many interesting hematological problems 

 involved. The most extensive work has been done on the lower 

 vertebrates and on human embryos. But, owing to the lack of 

 some of the most important stages and due to the poor preserva- 

 tion of much of the material, the work on the human fetus has 

 contributed little toward the solution of the many hematological 

 problems. 



For the following study the writers have selected the pig and 

 other mammalian embryos, because the material could be obtained 

 easily in all the desired stages. Special consideration was given 

 to the following problems: 1) the origin of the splenic rudiment, 

 especially its relation to the peritoneal epithelium; 2) the origin 

 of the first free cells of the organ; 3) hematopoiesis in the early 

 spleen and the origin of the first cells belonging to the 'myeloid' 

 series; 4) influence of enviromental factors on the hematopoietic 

 process; 5) development of the arteries and their surrounding 

 lymphoid sheaths; 6) development of the follicular tissue (white 

 pulp) and the origin of its lymphoid cells; 7) relationship between 

 follicular tissue and spleen pulp (red pulp) ; 8) comparison of the 

 hematopoietic process of the early spleen with myeloid metapla- 



. 279 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 28, NO. 2 



