Rotfnl Society, 



p^piffby'MtjloyiH^thd tWd'Iegs of ihe itistfwitl^nt' as i^uletk "A^ de- 

 scription referring to a diagram is given of this portable sextftht/' -^^ 

 ** Observatioti^dn the Growth and Dey^opwient of thft EjftAfer- 

 misi" By Era^mtta WilsOri,' Esq., F.lLS*iiEj€tetiii^ir'flfl!^ttatdttit'a»* 



Physiology ifi'the Middlfesei Hospital.' '•' f r 1 nr.wnf'n n vfVh^i.u^. 



' The author adduecS evidence derived from his niidroseopic obsei*-- 

 vations, in confirmation of the commonly received doctrine l-espect- 

 ing the origin of the cells of the epidermis and epithelium generally, 

 from the materials filfnijihed by the liquor sahguinis or plasma of 

 the blood; which fluid; pas^irig by eiidosniosfs through the walls' of 

 the capillary vessels and peripheral boundary of the sut-fa6e, deVfii 

 lopes grahules by a Vital process, tinalbgdus to coagulation, 0\\ ft* 

 careful exatnination of ' the Inrief surface of the epidermis with the 

 aid of the microscope, he finds it to be composed of four kind^ of 

 elements, arranged in such a ttianher as to constitute an irregular 

 platie, Similar to a tesfeelated of mosaic pavement. These elements 

 are,— 1. Gramtles, which the author tevms, primitive, of a globular' 

 form, solid aiid apparently homogeneous, and measuring about 

 l*20,000th part of an inch in diameter. 2. Aggregated gtamdes^ 

 having about double the diameter of the former and apparently com- 

 posed of as many of these as can be aggregated together without 

 leaving an unoccupied sjiace in the centre of the mass. 3. Nucleated 

 gmrntks measuring in diameter from the 6()00th to the 4000th part 

 of an inch, each being composed Of an aggregated granule as a 

 nucleus, enveloped by a single layer of aggregated granules, giving 

 to the whole mass an oval ot circular, and at the same time flat- 

 tened shape. Their constituent granules have acquired, during this 

 aggregation, greater density, and are separated from each other by 

 distinct interstitial spaees filled with a transparent homogeneous sub- 

 Stance* 4i Nucleolo'-nUcleolated cells pervading tlie deep stratum of 

 the epidermis, and of Which the longer diameter measures from th^ 

 3000th to the 2500th part of an inch. These cells, which constitute 

 the principal portion, and may be regarded as the chief constituent 

 of the epidermis, are formed from the nucleolated granules, on the ex- 

 terior of which there is superposed a transparent layer, bounded by a 

 well-defined outline, by the dark interstitial substance of the wall of the 

 cell ,• the nucleolated granule being the nucleus, and the aggregated 

 gt-anule the nucleolus of these primitive cells of the epidermis. The 

 author is of opinion that the nuclei, up to a certain point, grow with 

 the cells, by the Separation of the original granules from tlie deposi- 

 tion between tliem of interstitial matter, and also by the cleavage of 

 the latter and the consequent multiplication of the granules. This 

 peripheral growth of the cells is totally different from the mode of 

 growth described by Schvvann, and explains the disappearance of the 

 nucleus in the scales of the epidermis. The observations of the 

 author lead him to believe that the same process of development and 

 of growth is foflowed In the epithelium as in the epidermis ; and he 

 offers evidence, showing that similar arrangements take place in the 

 cells of melanosis, in the pigment cells of the choroid membrane of 

 the eye, and in those of the skin of the negro. 



