PROSRESS OF MICROSCOPICAL SCIENCE. 129 



fibres of insects whicli have died spontaneously or whicli have been 

 treated with water, very diluted saline solution, or diluted alcohol. 

 In most cases, however, especially in locustida amongst insects, and in 

 vertebrate animals in general, the disintegration takes place through 

 all the disks of the individual divisions ; in this way the so-called 

 primitive fibrils make their appearance. On observing the optical 

 longitudinal section of a fresh muscular fibre for some time, the disks 

 of the divisions, at first absolutely homogeneous, show immeasurably 

 fine pale isotropous longitudinal lines ; they are in almost regular 

 distances from each other, not more than 0*001 of a millimetre. 

 These lines gradually become brighter, and at the same time broader 

 — their thiclmess exceeding the • 0005th part of a millimetre — at the 

 expense of those parts that lie between them, without the muscular 

 fibre, as a whole, altering in diameter. Consequently it may be said, 

 that the appearance of the longitudinal bright lines is caused, not by 

 the swelling of a pre-existent intermediate substance, but by the 

 shrinking, i. e. coagulation, of elements, which have been previously 

 in close contact with each other ; so that all the disks of the muscular 

 division must be regarded as consisting in the living state of prismatic 

 elements, which are so swollen that they touch each other completely, 

 and which possess different chemical and physical properties in the 

 different disks, but the same properties in the same disk. An inter- 

 mediate fluid substance is not pre-existent, but is pressed out by those 

 elements when they coagulate. In a second paper,* Englemann treats 

 of the changes of the individual disks of the muscular division during 

 contraction of the muscular fibres. For studying these, Englemann 

 uses, like Flogel, perosmic acid. The living muscular fibre is dipped 

 into a solution containing * 5 to 2 per cent, of this reagent for a few 

 seconds ; it is then transferred into a ^ per cent, saline solution, which 

 is afterwards replaced by alcohol in a slightly rising concentration 

 (50 to 90 per cent.), and is finally placed in turpentine. The conclu- 

 sions which Engelmann draws from his observations are briefly these : — 



(a) The shortening force has its seat exclusively in the anisotropous 

 layer ; this latter thickens itself much more than the isotropous. 



(b) The isotropous substance decreases, the anisotropous increases 

 in volume during contraction ; it must be therefore assumed that fluid 

 which is expressed by the isotropous is imbibed by the anisotropous 

 substance, viz. the latter swells, the former shrinks during con- 

 traction. 



(c) The isotropous substance becomes darker, more opaque, the 

 anisotropous brighter, more transparent, during contraction ; the 

 median disk, however, does not become brighter. From this it may 

 be deduced that 



(d) The isotropous substance becomes firmer, the anisotropous 

 softer, dui'ing contraction. 



Mr. Schafer's views, having been already given in this Journal, 

 need not now be repeated. 



Condition of the Blood in Yellow Fever. — A long paper appears on 

 this subject, by Professor Joseph Jones, M.D. (U.S.A.), in the ' New 

 * Ibitl., vol. vii., parts 2 and 3. 



