The Microscope. 113 



has taken place. The abdomen is laid open, the uterus and oviducts 

 dissected and spread out, and careful search made with a lens for 

 the eggs, which are removed and hardened. 



A COURSE IN ANIMAL HISTOLOGY. 



FRANK W. BROWN, M. D. 



SECOND PAPER. 



/^ELLS AND INTERCELLULAR SUBSTANCES.— As histol- 

 ^-^ ogy deals with cells and intercellular substances, their forms, 

 stracture and aiTangements in the various organs and tissues, a few 

 general points concerning their forms and structure will be helpful as 

 an introduction to the more complicated study of their arrangement. 



Cells. — To one particular as to the use of words the name 

 " cell " as applied to the anatomical units of an organ is an unfor- 

 tunate one. The name was given at a time when our knowledge 

 was imperfect, and is still retained, though attempts have been made 

 to replace it with something more correct. Cella, a closet or store- 

 room, implies an inclosed space, and a cell was defined as a little 

 body inclosed by a membrane and composed of a soft or fluid 

 substance. This idea was formed from a histological study of 

 plants, and the name " cell " can still be considered as correctly 

 applied to the units of most vegetable tissues. In the animal king- 

 dom, however, the case is different. None of the anatomical units 

 are cells, as they possess no space-inclosing membrane, but are 

 solid masses of matter. The name " cell " will, however, be employed 

 in these papers, as, being the term in general use, it will create no 

 confusion. 



A typical cell (Fig. 1.), as described by the old masters, is a 

 spherical or spheroidal body composed of a cell-wall (A) inclosing 

 a soft, granular substance, the cell-body -]>^ 

 (B), imbedded in which is a much ""'-^^^ 

 smaller, more delicate cell, the nucleus q^ 

 (C). This nucleus may in turn contain 

 another delicate cell, the nucleolus (D), 

 and this latter may rarely contain still 

 another, the nucleoleolus. The cell- 

 wall is generally homogeneous, that is, X 



without any apparent structure, or it may have a delicate striated 

 or fibrillated appearance. The cell-body is composed of small 

 granules imbedded in a semi-fluid, colorless, homogeneous sub- 



