DEVELOPMENT OF CELLS. 



minute globules of oil when brought into contact with liquid albumen, 

 become at once invested by a coherent layer of the albuminons substance, 

 and thus acquire a vesicular character. 



On comparing the above two modes of cell-development with the 

 account furnished by Schwann, it will be observed that there is no striking 

 difference between them ; the first plan of development described by 

 Henle agrees essentially with that stated by Schwann, while between 

 Henle's second plan and Schwann's explanation of the origin of the cells 

 containing two (or more) nucleoli, the difference is more apparent than 

 real, and is not in either case founded on direct observation. The chief 

 discrepancy in the accounts of these two observers, appears to consist first 

 in Henle's disinclination to admit the existence and importance of nucleoli, 

 though, as before observed, there is no good reason for regarding the 

 nucleoli as structures dissimilar from Henle's elementary particles or 

 granules ; and secondly, in respect of the manner in which the cell-wall is 

 developed around the nucleus. 



In Henle's third mode of the development of cells, a large quantity of 

 the elementary granules arrange themselves together into a more or 

 less spherical mass, around which a delicate cell-wall is subsequently 

 formed; but it is not until a later period, if at all, that a nucleus can 

 be perceived in the midst of this mass. Illustrations of this mode of 

 development are presented by the large granular bodies met with in the 

 first milk or colostrum, by the so-called compound inflammation- or exuda- 

 tion-corpuscles, and by many of the globules found in malignant tumours 

 and other morbid products.* 



* It should be remarked, however, that doubts are entertained by several physiologists, of 

 the above being the mode in which the granular exudation-corpuscles found in the products 

 of inflammation, or in other diseased structures, are developed. Vogel (Pathologische 

 Anatomic des menschlichen Korpers, p. 127) is of opinion that these corpuscles are cells 

 which have an origin exactly similar to that described by Schwann, as occurring in the 

 development of other nucleated cells ; and he believes that they only subsequently assume 

 the granular condition. Reinhardt (Archiv fur pathologische Anatomie und Physiologic, by 

 H. Virchow and B. Reinhardt, 1847,) entertains an almost exactly similar view, and he 

 believes that the exceedingly granular condition of exudation-corpuscles and of other granu- 

 lar-looking cells, is probably always a later change due to the formation of granules of fat, 

 and just precedes the cessation of their period of life, which event is manifested by the 

 disappearance of the nucleus and cell wall, and by the breaking up of the cell into an irregular 

 heap of granules. He believes also, that these retrograde changes take place in cells 

 developed under normal as well as abnormal conditions, and he furnishes many examples in 

 proof of this. The best of these examples is afforded by the changes which ensue in the 

 cells composing the membrana granulosa of the Graafian follicle during the degeneration 

 which the follicle undergoes in the ovary. These cells; in the mature Graafian follicle, are 

 nucleated, and filled with tolerably clear albuminous contents ; but as the follicle degenerates 

 or retrogrades, the cells become opake from the formation of granules or particles of fat 

 among their contents, the nucleus disappears, and ultimately the more or less thick yellowish 

 substance filling the follicle, is found to consist almost entirely of granule cells (like exuda- 

 tion-corpuscles) and heaps of granules, into which the cells have broken up. On the other 



