PUT FORTH BY VALENTIN. 223 



Pigment-globules of a black colour are soon, however, developed on 

 their periphery, so that the corpuscles or vesicles jusl mentioned are 

 transparent in their centre when they have ceased to be so, and have 

 become dark on their circumference. It is plain that von Ammor) and 

 R. Wagner have seen this condition as well as myself. The globules 



are so small from the commencement, that they This proc 



of deposition of the black-coloured globules upon the pigment-cor- 

 puscles goes on afterwards continuously, and to such an extent that 

 the latter are enveloped and covered on all sides by them, and are only 

 rendered visible when the globules are removed by pressure or washing.); 

 and I compared the pigment-cells with the cellular tissue of 



plants. (Repertor. ii, 245. The pigment here (in the choroid) has 

 the same character which it has in most other parts of the body, that 

 is, a round, clear, transparent, and colourless nucleus, or the pigment- 

 molecules lie closely crowded together around a pigment-vesicle. These 

 heaps of pigment composed of pigment-vesicles, and the molecules of 

 pigment deposited around them, are extended outsidewise, and in man, 

 the dog, the rabbit, the horse, the ox, and such like, form unequal 

 pentagons or hexagons, w r hich are placed close together in a similar 

 manner to the cells of the parenchymatous cellular tissue of plants. 

 Langenbeck de retina, 38.) Schwann gave an essential complete- 

 ness to these analogies, by showing that the gelatinous primordial 

 mass of the tissues ivas composed of cells, that the bodies im- 

 bedded in it are nuclei, and that these and the cells oft <n exhibit 

 analogous laws of development. (Froriep's Notizen, 1838, 

 Mikroskopische Untersucliungen iiber die Struktur dor Tbicre 

 und Pflanzen, Heft i, 1838.) As early as 1837 / had observed 

 the cells of the germinal membrane in the ovum of sepia, with 

 their nuclei and nucleoli, and the areas surrounding them, and 

 had communicated my researches in a letter to Breschet. Shortly 

 after 1 became acquainted with Schwann's first communication I 

 commenced the investigation of the subject. The chief results 

 of my inquiries are contained in the following communication. I 

 have, at the same time, referred to the correspond///// passages 

 in the first part of Schwann's treatise, which I have received 

 this day. ,} 



I will only add that the second part also, (consisting of sh< i 

 8 to 13, and Plates III and IV,) therefore the whole of the 

 portion of my treatise containing the observations, had appeared 

 previous to Valentin's researches, and had been communicated to 

 the Parisian Academy in the year 1838; a remark which docs 

 not appear altogether superfluous, since Professor Wagner has 



