2 CLARKE, ON STRIPED MUSCULAR FIBRE. 
another fibrilla or row of particles. But even when the sur- 
face of the fibre is perfectly plain, with the exception of the 
two lateral borders, it may be resolved into fibrille by the 
influence of certain reagents, particularly chromic acid. 
The diameter of the same fibre varies at different parts of 
its course, and the nuclei it contains are located at variable 
distances from each other. Sometimes, however, three or 
four are heaped closely together, one overlapping the other ; 
and sometimes two are in contact at their edges, having just 
undergone the process of division. The fibres arrange them- 
selves side by side, with the nuclear enlargements of one a 
little above or below those of another, so that their respective 
curvatures admit of their lying in close contact. Pl. I, fig. 19 4 
represents three fibres disposed in this way, but intentionally 
separated a short distance from each other. Sometimes they 
may be seen to increase in diameter or in the number of 
fibrille by the adhesion of fresh nuclei, from which new 
granular processes of blastema extend along their edges 
(fig. 20a, 6). Each of their lateral borders constitutes one 
fibrilla or more; but, except under the influence of chromic 
acid or some other reagent, it is only occasionally that the 
fibrillee are resolved into particles or granules, which are in 
some cases exceedingly fine (see fig. 19 a). 
The muscular tissue of the heart in the same foetus differed 
in some respects from that of the trunk. The free nuclei 
were more densely crowded together, but the granular blas- 
tema was less abundant. All these bodies gave off processes, 
which, in many instances, were mere fibres, but in others 
they were broad at their attachment to one side or end of 
the nucleus, from which they tapered off into fibres, so as to 
present a funnel-shaped appearance (see fig. 21 @).* During 
the first formation of the muscular fibres the nuclei, with their 
processes, were disposed side by side, as represented in fig. 
216. When formed, they were, in general, more uniformly 
granular than those of the trunk, more varied in shape, and 
irregular in breadth, and gave off branches by which they 
were connected in a kind of plexus or anastomosis. In some 
cases they were joined together by broad expansions of con- 
densed blastema (something lke the webb in a frog’s foot), 
in which much finer branches might be frequently seen in 
* From their appearance there is reason for believing that these funnel- 
shaped bodies are rudimentary nerve-cells in the substance of the heart ; for 
they bear a striking resemblance to the rudimentary cells which I found in 
the intervertebral ganglia of the foetus (see ‘Phil. Trans,’ for the present 
year, 2nd part). Some of the fusiform bodies belong to the tendinous tissue, 
and are of stronger outline than the others. 
