XV111 



PRODUCTION OF CELLS. 



So far the process is the same as before ; but now a species of capsule is 

 formed round each of the young cells (B), whilst the old one enclosing 

 them becomes blended with the intercellular matrix, and is no longer 

 traceable (c). 



Fig. XII.- IDEAL PLAN OF THE MULTIPLICATION OF CELLS OF CARTILAGE. 



A, cell in its capsule ; B, divided into two, each with a capsule ; C, primary capsule 

 disappeared, secondary capsules coherent with matrix ; D, tertiary division j E, secon- 

 dary capsules disappeared, tertiary coherent with matrix. 



The new cells, in turn, divide in the same way, so as to make a 

 group of four, each of which is surrounded by its own capsule (D), whilst 

 the capsules of the first descent (secondary) blend with the matrix (E) like 

 their predecessor. In certain cases the whole series of capsules may 

 remain visible ; in others, and especially in morbid conditions, the young 

 capsules may not be formed, or may all disappear, leaving the young cells 

 surrounded by the still conspicuous original capsule, like the yelk-segments 

 in the ovum. 



The multiplication of cells in the ovum and in cartilage, seeing that it takes place 

 within an enclosing envelope, has been named " endogenous ; " but it will be per- 

 ceived that the difference between this and the division of a free cell is unimportant. 



d, Multiplication of Nuclei in Cells. Irregularly shaped cells have been 

 found in the medullary cavities of bone (Robin and Kolliker), containing 

 many nuclei, and such cells afford an example of the multiplication of 

 nuclei within a cell without separation into new cells. Other multi- 

 nucleated cells are formed in the spleen and pass into the blood of the 

 splenic vein (Kolliker); but if these eventually divide into uninucleated 

 cells, as seems most probable, the case falls under 6, 2. 



e. Multiplication of free Nuclei. Bodies having the characters of nuclei 

 and designated as such, commonly make their appearance in large numbers 

 where growth or new formation of tissue is going on. There can be little 

 doubt that these are produced by division of previously existing nuclei, 

 uninclosed in cells but yet originally descended from cells, and probably 

 associated with an inconspicuous amount of shapeless protoplasm. The new 

 nuclei may continue in the same condition as those from which they imme- 

 diately sprung, or it may happen that the protoplasm grows and accumulates 

 round the groups of multiplying nuclei, each of which assumes its distinct 

 share, and there thus results a group of new cells. The nuclei lying on the 



