190 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 



of the growth of the bone in length. There are, however, 

 certain exceptions (vertebral apophyses), 



" In the last paragraph of this paper l^olliker produces a 

 new scheme for explaining the growth of long bones. For 

 this, however, we must refer the reader to the paper itself." 



Kolliker's important researches, which we have already 

 referred to, are now published in a complete form, with eight 

 plates and many additions (' Die Normale Resorption des 

 Knochengewebes,' Leipzig, 1873, 4to, pp. 86). 



4. Histogenesis of bone. — Strelzoft' (' Eberth's Untersuch- 

 ungen,' Zurich, 1873, pp. 64, four plates) has published some 

 elaborate researches on the histogenesis of bone, beautifully 

 illustrated, contradicting in some points those of KoUiker. 



VI. Muscle. — 1. Structure of voluntary muscle. — Krause 

 ('Pfliiger's Archiv,' 1873, vol. vii, pp. 508—514) discusses 

 the contraction of muscle fibres and the apparent reversal of 

 the characters of the singly-refracting and doubly-refracting 

 substance, as to darkness and lightness {' Umkehrung ' of 

 Engelmann) of which he gives a different interpretation 

 from any arrived at by other observers. 



Wagoner (' Schultze's Arcliiv,' vol. ix, p. 712) concludes 

 that in striated muscle the fibrilla is the ultimate element of 

 the fibre ; that all the forms of transverse discs take their 

 origin only out of the subdivision of the contractile substance 

 in different parts of the fibrilla ; and that the intermediate 

 discs are not definite structures. 



The observations of Engelmann and Schafer are thus 

 summarised by Klein (' London Medical Record,' 1873, pp. 

 647 and 665) with those of other observers already noticed 

 in this journal: 



"T. W. Engelmann describes his microscopical observa- 

 tions on the striped muscular tissue in ' Pfliiger's Archiv,' 

 vol. vii, part 1. He studied the striped muscular fibres of 

 arthropoda. They were observed in a moist chamber with- 

 out the addition of any reagent, for reagents produced very 

 marked changes. The fibres were in a perfectly fresh and 

 living condition, showing still very lively contractions. 



" Each muscular fibre is divided into a number of divisions 

 of equal sizes by transverse dark membranes — intermediate 

 discs, which are closely united with the sarcolemma. Each 

 division contains in the centre a bright, slightly refractive 

 transverse median stripe — median disc of Hensen, on each 

 side of which lies a dim, highly refractive band — the trans- 

 verse disc ; then comes on each side a bright, slightly 

 refractive band — isotropous substance ; then a dai'k, highly 

 refractive stripe — the lateral disc ; and finally, again, a thin. 



