26 STRUCTURE AND GROWTII 
dark side in the thickness of the walls distinguished. The 
delineation, at the same time, proves how important a share is 
taken by the intercellular substance in the formation of the 
firm structure of cartilage. 
The cartilages of the foetus do not altogether accord in chemi- 
cal constitution with those of the adult, since we can obtain from 
them by boiling but a small quantity of a gelatinous substance, 
and that only with great difficulty, and they afford no true 
gelatine (capable of forming a jelly). I boiled some unossi- 
fied cartilages, consisting of apophyses of the femur and carti- 
laginous portions of the scapule, taken from several embryo 
pigs, measuring three and a half inches in length. After 
twelve hours’ boiling, they entirely crumbled into very small 
scales, which gave a variegated appearance to water im which 
they were stirred about, and appeared under the microscope 
extremely thin and granulous. The fluid, when filtered and 
evaporated almost to dryness, did not coagulate. Alcohol pro- 
duced a copious precipitate, which was dried, afterwards dis- 
solved in boiling water, and then evaporated almost to dryness; 
still no coagulation took place. Alum, however, clouded the 
fluid, and acetic acid had the same effect, but in a much 
slighter degree. As the quantity of cartilage made use of in 
the foregoing experiment was too small, I made a further in- 
vestigation with cartilage which had already become ossified, 
from the same embryos, namely, the frontal and parietal bones, 
scapule, humerus, femur, and some ribs. The unossified parts 
were removed as cleanly as possible from al] the bones. The 
earthy matter was withdrawn by hydrochloric acid; the carti- 
lages were then washed with water, and boiled for twenty-four 
hours. Under this process they fell to pieces very slowly , 
meanwhile numerous little glittermg scales appeared in the 
fluid, which, after beimg dried, resembled very minute fish- 
scales, and exhibited a beautiful play of colours. They were, 
perhaps, the lamellee described by Deutsch, which surround the 
minute medullary canaliculi. The form of most of the pieces 
of cartilage remained perfectly recognizable, and was but 
slightly altered. They looked of a yellowish-white colour, and 
not at all gelatinous, as substances usually do when about to 
be transformed into gelatine. The fluid was filtered from these 
little scales and pieces of cartilage, and then evaporated almost 
