274 SPECIAL HISTOLOGY. 



or four or even six, either contiguous or arranged serially. 

 From this period to that of birth, no further important change 

 takes place in the muscular fasciculi, except an increase in their 

 size. In the new-born infant they measure O0056 — O0063"', 

 are solid, rounded, polygonal, longitudinally or transversely 

 striated, according to circumstances, as in the adult, with 

 very readily isolated fibrils, and no longer any appearance of 

 nuclei. 



From what has been remarked, it is clear, that the sarcolemma 

 represents the sum of the membranes of the coalesced cells, 

 and that the nuclei of the youngest fasciculi are the original 

 cell-nuclei, whose descendants are represented in the nuclei of 

 the older fibres, which have multiplied by an endogenous 

 process. The muscular fibrils are the altered contents of the 

 original tubes, become solid ; they appear, demonstrably in 

 many instances, to be formed on the inner surface of the 

 sarcolemma, from without to within, but in other cases probably 

 in the whole of the tube at once. 



The growth of the entire muscle is chiefly to be referred to 

 the increase, both longitudinal and in thickness, of the primitive 

 fasciculi; and the rudiments of all the future primitive fasciculi 

 appear to be formed, probably even as early as the original 

 rudiments of the muscle itself — in every case at the middle 

 period of foetal life. In the embryo, at the fourth or fifth 

 month, they are perhaps five times as thick as in one at two 

 months ; in the new-born infant they measure for the most 

 part twice, occasionally even three and four times as much as 

 in the fourth and fifth month, and in the adult their size is 

 perhaps five times greater than in the new-born child. The 

 number of fibrils must necessarily increase in proportion to the 

 size of the fasciculus, because, according to Harting, they are 

 but little thicker in the adult than in the foetus. The 

 perimysium is developed, as I find in agreement with Valentin 

 and Schwann, after the type of the common connective tissue, 

 from fusiform, coalesced formative cells. 



The elementary parts of the tendons are, in no case, formed 

 earlier than those of the muscles; for, in embryos from the 

 eighth to the ninth week, I have never been able to detect a 

 trace of them, although at this time the muscular fibres are 

 quite distinct. It is not till the third or fourth month, when, 



