The Ergastoplasm in the Mammary Gland 

 and Its Tumours: 

 An Electron Microscope Study with Special Reference to 

 Caspersson's and Santesson's A and B Cells 



F. Haguenau and K. H. Hollmann 



Lahoyatoire de Mcdecine Experiniciita/e dii College de France, 

 Paris, France 



To all cytologists nowadays, the ergastoplasm is a well-defined entity, 

 the ultrastructure of which may be considered as characteristic ([i, 2], and 

 Porter this volume). Its particular importance lies in the fact that it 

 corresponds to the cytoplasmic nucleic acid (RNA) and is directly involved 

 in protein synthesis. In spite of much knowledge acquired during the last 

 few years the meaning of some ultrastructural aspects of ergastoplasm still 

 escapes our understanding. It is our purpose, by taking the example of 

 the mammary gland, to comment upon these aspects because though they 

 are mentioned and acknowledged by many they ha\e not yet sufficiently 

 been put forward. 



At the onset we wish very briefly to go back to the question of nomen- 

 clature. Contrary to what might have been expected from the confused 

 situation which reigned at the beginning, agreement has been reached 

 between cytologists and, most of the time, the same terms are being used 

 now to design the same constituents : 



Ergastoplasm: System of intracytoplasmic membranes characterized by 

 the presence of granules attached to its outer surface. 



''Organized'' Ergastoplasm: Such a system when abundant and more or 

 less arranged in parallel array. 



''Endoplasmic Reticulum'': Membrane component of this system (con- 

 tinuous with other intracytoplasmic membranous organelles in the cell 

 especially the Golgi apparatus). 



Ribonucleoprotein granules (RNP-granules, " Ribosomes ") : The granular 

 component of ergastoplasm either membrane-attached or isolated in the 

 ground cytoplasm. The following diagram will be helpful : 



