570 POPULAR SCIENCE MONTHLY. 



of the yolk were successfully demonstrated. In a third memoir, pub- 

 lished in 1841, Barry definitely stated that young cells originated 

 through division of the nucleus of the parent cell, instead of arising, as 

 a product of crystallization, in the fluid cytoblastema of the parent cell 

 or in a blastema situated external to the cell. 



In a memoir published in 1842, John Goodsir advocated the view 

 that the nucleus is the reproductive organ of the cell, and that from 

 it, as from a germinal spot, new cells were formed. In a paper, pub- 

 lished three years later, on nutritive centers, he described cells, the 

 nuclei of which were the permanent source of successive broods of 

 young cells, which from time to time occupied the cavity of the parent 

 cell. He extended also his observations on the endogenous formation 

 of cells to the cartilage cells in the process of inflammation and to other 

 tissues undergoing pathological changes. Corroborative observations 

 on endogenous formation were also given by his brother, Harry Good- 

 sir, in 1845. These observations on the part which the nucleus plays 

 by cleavage in the formation of young cells by endogenous develop- 

 ment from a parent center — that an organic continuity existed between 

 a mother cell and its descendants through the nucleus — constituted a 

 great step in advance of the views entertained by Schleiden and 

 Schwann, and showed that Barry and the Goodsirs had a deeper insight 

 into the nature and functions of cells than was possessed by most of 

 their contemporaries, and are of the highest importance when viewed 

 in the light of recent observations. 



In 1841 Robert Eemak published an account of the presence of two 

 nuclei in the blood corpuscles of the chick and the pig, which he re- 

 garded as evidence of the production of new corpuscles by division of 

 the nucleus within a parent cell; but it was not until some years after- 

 wards (1850 to 1855) that he recorded additional observations and 

 recognized that division of the nucleus was the starting-point for the 

 multiplication of cells in the ovum and in the tissues generally. 

 Remak's view was that the process of cell division began with the cleav- 

 age of the nucleolus, followed by that of the nucleus, and that again by 

 cleavage of the body of the cell and its membrane. Kolliker had pre- 

 viously, in 1843, described the multiplication of nuclei in the ova of 

 parasitic worms, and drew the inference that in the formation of young 

 cells within the egg the nucleus underwent cleavage, and that each of 

 its divisions entered into the formation of a new cell. By these ob- 

 servations, and by others subsequently made, it became obvious that the 

 multiplication of animal cells, either by division of the nucleus within 

 the cell, or by the budding off of a part of the protoplasm of the cell, 

 was to be regarded as a widely spread and probably a universal process, 

 and that each new cell arose from a parent cell. 



Pathological observers were, however, for the most part inclined to 



