116 
DR. MARTIN BARRY ON FIBRE. 
duct. And the observation now recorded, that these structures consist of the remark- 
able filaments in question, seems sufficient of itself to warrant the belief that they 
have no such mode of origin. 
116. I have already mentioned having seen these filaments in the shell-membrane 
of the Bird’s egg. This membrane I believe is usually regarded as the analogue of 
the chorion in Mammalia. Now the chorion of the Mammal, according to my ob- 
servations, has its origin in corpuscles of the blood : and it is not likely that its ana- 
logue in the Bird is produced in a different way. 
13 7- On a former occasion'!', we saw the incipient chorion, when rising from the 
“ zona pellucida” in the mamtniferous ovum, to leave a stratum of unappropriated 
cells behind it on the “zona,” a gelatinous fluid intervening. These cells are sub- 
sequently appropriated in the thickening of the chorion. I think it possible that it 
may be the outer layer of the chorion just mentioned, that is represented by the shell- 
membrane ; while the stratum of cells left for a while on the “ zona” in the mammi- 
ferous ovum, finds its analogue in the chalazee of the Bird’s egg. If so, it will doubt- 
less be found that the chalazee also have their origin in corpuscles of the blood ; which 
indeed their structure renders probable. 
118. As already mentioned (par. 53^), many of the figures which accompany the 
foregoing memoir represent states of voluntary muscle, in which the longitudinal 
“ fibrillse” have no concern in producing the transverse striae. In these states, the 
transverse striae are caused by comparatively large interlacing spirals, which dip 
inwards in a manner that may be represented by making the half-bent fingers of the 
two hands to alternate with one another, and then viewing them on the extensor side. 
The longitudinal “ fibrillse” are contained within the spaces circumscribed by the 
interlacing spirals. 
119. It is in such states of voluntary muscle, that the fasciculus “breaks off 
short (fig. 157)-” This breaking off short is a natural consequence of the interlacing 
of the spirals ; as may be easily shown by a wire model, representing this state of the 
fasciculus. The fracture of course takes the direction in which there is the least 
resistance. This direction is the transverse, for in any other there would be a greater 
number of the curves of spirals to be encountered^. Sometimes the fasciculus, 
instead of being “broken off short,” is merely notched (fig. 157). These two effects 
of manipulation, however, differ only in degree; the cause producing both being the 
same §. This seems to he the explanation of transverse “ cleavage .” 
f Supplementary Note to a Paper entitled “ Researches in Embryology. Third Series : a Contribution to 
the Physiology of Cells.” Philosophical Transactions, 1841, Part II. p. 193. 
I When the longitudinal striae are exceedingly distinct, the fasciculus does not “ break off short.” This 
appears to be owing to the absence now of the investing spirals ; which, when present as such, regulate the 
direction of the fracture. I have already stated them to pass into a membranous form. 
§ Occasionally the extremities of the ruptured spirals (figs. 156, 157) maybe seen pendent at the part where 
the fasciculus is broken off or notched. 
