138 



OF THE STRUCTURAL ELEMENTS OF THE HUMAN BODY. 



out (toe. cit.), that the cell-wall of secreting cells is much less perfectly formed 

 than that of the cells which are to remain as components of the solid tissues, and 

 has a much greater tendency to deliquescence, whereby the contents of the cell 

 are set free. Again, the presence of nuclei appears to exert an influence, as 

 will be presently shown, on the production of fibres in the midst of an organiza- 

 ble blastema ; and there seems reason to think, also, that the yellow or elastic 

 fibres are formed by the linear extension of the nuclei themselves ( 224). 

 Some forms of basement-membrane, too, seem to be composed of aggregations of 

 nuclear particles, which not improbably serve as the instruments of promoting 

 vital operations in organizable fluids in their proximity. These facts concur with 

 those already cited ( 102), to support the view that the nucleus is that compo- 

 nent of the Cell through which its peculiar powers are chiefly exerted. 



118. Of Simple Fibres; their Formation and Properties. That all the 

 Animal tissues have their origin in Cells, so that even the widest diversities of 

 type are reducible to the same category, was the doctrine originally put forth by 

 Schwann, who first attempted to generalize the phenomena (most of them dis- 

 covered by his own observations) which are presented by their development. 

 By subsequent research, however, it has been shown that this statement was too 

 hasty } and that, although many of the tissues retain their primitive cellular 

 type through life, and many more are evidently generated from cells which sub- 

 sequently undergo metamorphosis, there are some in which scarcely any other 

 cell-agency can be traced than that concerned in the preparation of the plastic 

 material. This would seem to be the case especially with those Simple Fibrous 

 Tissues, hereafter to be described (CHAP. v. SECT. 1), which make up a very 

 considerable proportion of the bulk of the body. For although it seems indu- 

 bitable that they may be formed by the transformation of cells, and although 

 they probably are thus generated in the first development of the organism, yet 

 their subsequent production (especially in the reparation of injuries under favor- 

 able circumstances) seems to be effected by the fibrillation of an " organizable 

 blastema" ( 26-28). Even here the course and direction of the fibres seem 

 often to be determined by the nuclear particles which the fibrillating substance 

 includes; for in the reproduction of tendinous tissue, as observed by Mr. Paget, 1 

 the nuclei are formed and become elongated before any fibrillation is visible, and 

 the fibrillation takes place in the direction in which 

 they lie, so that each nucleus is imbedded in a fasci- 

 culus of fibres; and a similar relation has been pointed 

 out by Mr. Addison, 3 who has remarked that the fibres 

 which are formed during the coagulation of the Liquor 

 Sanguinis or in other plastic exudations, often seem 

 to radiate from the cells or nuclear corpuscles which 

 these fluids may contain (Fig. 10). These facts give 

 a sufficient explanation of the presence of nuclei in 

 the midst of the simple fibrous tissues, which has 

 been adduced in support of the doctrine of their ori- 

 gin in cells. A very marked example of the produc- 

 tion of fibres in the midst of an organizable substance, 

 without any direct intervention of cells, is afforded 

 by Fibro- Cartilage ; the various forms of which pre- 

 sent every gradation between the perfectly homoge- 

 neous intercellular substance of ordinary Cartilage 



Fig. 10. 



Cells with radiating Fibres, from 

 the fluid of the vesicles of Herpes 

 labialis. 



1 "Lectures on the Processes of Repair and Reproduction after Injuries," in "Medical 

 Gazette," 1849, vol. xliii. p. 1071. 



2 " Second Series of Experimental Researches on the Process of Nutrition in the Living 

 Structure," p. 5 ; and "Third Series," p. 7. 



