550 DEVELOPMENT OF THE SIMPLE TISSUES, BY S. STRICKEB. 



chief and the intermediate substances alternate in breadth ; the 

 form of the limiting surfaces of the two varies, so that the in- 

 termediate substance sometimes exhibits a nodal point, some- 

 times again an attenuation. The position of the disks, as 

 regards the vertical line, also varies, being sometimes oblique, 

 sometimes plane and vertical. Moreover, each zone does not 

 implicate the whole surface or the whole area of a transverse 

 section : displacements sometimes occur, giving the impression 

 that one half of the fibre has been shifted about half the 

 breadth of a disk, occasioning the limiting line between the 

 chief and intermediate substance to be interrupted or to be 

 angularly curved. 



Other fibres appear transversely and longitudinally striated, 

 the longitudinal striation sometimes traversing both substances, 

 and sometimes being limited to the chief substance. Other 

 fibres, again, appear only longitudinally striated ; and others, 

 again, neither longitudinally nor transversely striated. There 

 is no doubt that all these conditions are presented by living 

 fibres. The course of a fibre which is neither transversely nor 

 longitudinally striated is rendered extraordinarily distinct, 

 and it may also be clearly seen how such a fibre suddenly 

 entirely or partially acquires transverse striation, and just as 

 quickly loses it again. In order to make this intelligible, I 

 can only refer to the image presented to the eye by a bird's- 

 eye view of a corps of infantry whilst actively engaged in 

 performing evolutions ; and as it sometimes inarches in more 

 or less deep columns, and appears with transverse bands of 

 variable breadth ; sometimes again formed into lines that are 

 disposed vertically to the direction of the columns ; and some- 

 times, lastly, form squares, in which the transverse and lon- 

 gitudinal striation disappear in order to reappear, one or both, 

 the next moment. Such appearances are, it is obvious, most in 

 accordance with the view that muscle consists of small groups 

 of disdiaclasts and a fluid intermediate substance. We must 

 not at the same time forget that there are many considerations 

 opposed to this view. 



It appears to me to be important to mention those work# 

 that are chiefly occupied with the muscular tissue as it appears 

 in the lowest forms of animals. Perhaps the works bearing 



