196 
On the Structure and Development of 
It is believed that tlie use of several nev^ metliods which do not 
appear to have been previously used in investigating the con- 
nective substances has helped to throw light upon these obscure 
subjects. The consideration of each tissue will be taken up in 
the order in which it has been tabulated. Some observations on 
development of connective substances will then follow. 
1 . Mucous Tissue. — It is well known that this substance is seen 
to great advantage in the umbilical cord of the embryo, and the 
following method has been found best suited to demonstrate it. 
Take a small piece of cord at about the third month and immerse 
it a few weeks in Miiller's fluid ; make a thin section through the 
very soft gelatinous part, then immerse it a few minutes in distilled 
water, to which subsequently a few drops of acetic acid are to be 
added, so that the solution shall not contain more than 1 per cent, 
of acid, and then mount in glycerine. It will then be seen that 
the softest portion contains numbers of irregularly shaped flattened 
plates, some containing an oval, flattened nucleus, others having 
none that are apparent (Fig. 2, Plate OLYI.). So me of these flattened 
bodies anastomose by these processes with those of other plates; 
others are quite free. The substance lying between the cells, the 
intercellular substance, is in the softest portions quite homogeneous 
or slightly granular, and has no marks of fibrillation. In the 
neighbourhood of the firmer tissue, lines of fibrillation occur, while 
at the same time these flattened bodies become smaller, though 
they are still flat.* The intercellular substance is distinguished 
by its chemical reaction, which distinguishes it from other albu- 
minoid substances. It difl'ers from albumen in not containing 
sulphur, from chondrin and gelatin in not being precipitated by 
boiling, tannin or the bichloride of mercury. 
The corpuscles appear to consist of an oval, flattened, central 
body, about which there is an extremely delicate and pale en- 
velope, that may or may not be connected with other similar 
bodies. These delicate bodies are smaller the nearer they are 
fouad to the firmer or fibrillated tissue, while as they diminish in 
size there appear under them certain areas of intercellular substance 
having the form of elongated and flattened bands, which, seen in 
profile, give to the whole the appearance of a spindle cell of which 
the flattened body is the nucleus (Fig. 3, a). That this is an 
illusion, however, may be judged from the fact that the flattened 
band will often be found to show the marks of fibrillation, and the 
flattened body may be seen to be simply superimposed on the band 
and not in it, for, by carefully brushing these tissues with a camel's- 
hair brush, after the prolonged use of Miiller's fluid as above 
mentioned, and the subsequent immersion in a solution of common 
salt (10 per cent.), the bodies may often be brushed away (h). 
* The intercellular substance in the figure is imperfectly represented. 
