DEVELOPMENT OF CONNECTIVE TISSUE. 89 



fibrils, fasciculi have also become developed. The peritoneum 

 of a human embryo at the fifth month permits a very clear 

 view to be obtained of the fascicular fibrils and fine elongated 

 fusiform cells (fig. 5). 



At a later period, however, there appear in man and certain 

 animals for example, in the dog, but not in the sheep larger 

 or smaller sharply defined foramina.* In human infants these 

 are much less numerous and much smaller than in adults, and 

 the fine striae of the surrounding fibrils may be here observed 

 running close to the margin of each foramen. 



If the process of development be further followed, as I have 

 done in the peritoneum of a child of one year old, and from 

 thence up to the eleventh year, we may observe that the num- 

 ber of the foramina in the membrane undergoes continuous 

 increase, and the fasciculi and bundles of fibrils augment in 

 thickness, which may be particularly well seen in the fibres 

 surrounding the foramina. It certainly cannot be observed 

 during this growth of the membrane that the fibrils originate 

 from the processes of the cells. 



If we pass from the examination of the peritoneum to the 

 tendons of ernbryoes, treated in a similar manner, much caution 

 must be used in drawing conclusions respecting the appear- 

 ances presented. 



In young embryoes, closely compressed roundish formative 

 cells may be found at an early period, containing as yet only 

 imperfectly differentiated nuclei. Such cells become, to some 

 extent, elongated in the direction of the long axis of the ten- 

 don, and their margins are not very well defined. The isolated 

 cells present the appearance of delicate flocculi in carmine prepa- 

 rations, with the deeply reddened nucleus in their centre. These 

 cells subsequently increase in point of length, as do also their 

 nuclei, the latter becoming at the same time more sharply 

 defined, clear at their margins, and presenting an elongated 

 mass of granules in their interior. The elongated cells appear 

 to be composed of a more strongly refractile substance than 

 the primitive cells, and are capable of being more easily isolated. 

 A clear, smooth intervening substance similar to that which 



* See Bruch, Zeitschrift fiir Rationelle Medicin, Band viii., fig. 1. 



