143 



cell-wall lined on its internal surface by a layer of elementary mole- 

 cules and granules : 2nd, an eccentric nucleus : and 3rd, more or 

 less solid or fluid cell-contents. 



In the majority of instances there is an additional layer of granular 

 matter on the exterior or free surface of the cell-wall. These 

 granules are rendered paler, but are not dissolved by acetic acid ;* 

 and their quantity appears to be increased on the addition of strong 

 ammonia. The action of acetic acid upon these cells and their con- 

 tents is much less strongly marked than is ordinarily the case in cells 

 bearing the same structural relations. The cell-contents are either 

 fluid or imperfectly solidified like gelatine : they are of an albumi- 

 nous character, and have elementary granules imbedded in their in- 

 terior. The nucleus is large, oval, slightly cupped, and marked by 

 two dark circumferential rings. It is possessed of two coats, — 

 an outer one, clear, structureless, and forming nearly two-thirds of the 

 whole thickness of the nucleus, and an inner one investing an aggre- 

 gation of dark, refractive, elementary granules. This body appeared 

 to resist the action of ordinary re-agents : dilute sulphuric acid alone 

 appeared to exert any effect upon it, and that, simply by render- 

 ing the central granules paler and less distinctly defined. 



As illustrative of the principal modifications of these general cha- 

 racters in respect to both the constitution and form of the cells, I sub- 

 join examinations of the mucus scraped from three different parts of 

 the body, — from the exterior of the mouth, from the middle of the 

 back, and from around the anal orifice. 



In the matters scraped from the exterior of the mouth there were 

 found, in addition to fluid mucus and elementary granules, three 

 different forms of epithelial cells : these were the ciliated, the tessel- 

 lated, and the caudate. 



The ciliated epithelial cells were from three to five times the dia- 

 meter of the human blood-disk, irregularly spherical, and analogous 

 in constitution to the same bodies as observed in all the lower classes 

 of the animal kingdom. Each cell was truncated, so as to form 

 an abrupt extremity, which retained its form by means of a ring 

 of elastic fibrous tissue to which the hollow pyramidal cilia were 

 attached. 



The tessellated epithelium occurred in the form of patches, the in- 

 dividual cells composing which were small — about -nnny of an inch 



* The cell-membrane strongly resisted the action of acetic acid : I could never dis- 

 solve it entirely by the use of this re-agent. 



n2 



