EXPLANATION OF THE PLATES. 



Fig. 4. A transverse section of the nail of the middle toe of 

 an adult magnified 100 diameters, showing its 

 lamellated structure, and the mode of its connexion 

 with the papillary layer of the dermis by mutually 

 interlocking processes. This mode of union is ex- 

 cessively firm, and is precisely that employed by 

 carpenters, and known by the appellation of " dove- 

 tailing." 



Fig. 5. A portion of epidermis removed from the back of 

 the neck by means of a blister, and magnified 670 

 diameters. The younger cells are seen to be filled 

 with a straw-coloured fluid, the serum extracted 

 through the agency of the vesicant. 



Fig. 6. A. Some detached cells of epidermis, obtained by 

 scraping the sole of the foot, magnified 670 diameters. 

 Cells in a similar state exist beneath the nails, 

 around the nipple, and on the surface of the body 

 of new-born children where the creamy scum formed 

 by them and intermingled with fatty matter poured 

 out by the sebacious glands has been named 

 Vernix caseosa. (See C.) B. Cells of some mag- 

 nified 130 diameters. D. Cells of epithelium from 

 the mouth of the Menobranchus lateralis : they are 

 introduced for the purpose of showing the accuracy 

 of the law of the relation in size of the several 

 elements entering into the composition of the animal 

 frame. E. Two or three epithelial cells of the 

 lateral ventricles of the brain. I have recently as- 

 certained that the epithelium of the frontal sinuses 

 is as stated, ciliated. I cannot help suspecting, 

 however, that it is not in all cases so. No amount 

 of care has succeeded in the detection of ciliary 

 epithelium in the ventricles of the brain. The epi- 

 dermis of tritons and frogs consists of hexagonal, 

 translucent, and adherent cells, containing distinct 

 granular nuclei. 



