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V. — On the Structure and Development of Connective Substances. 
By Thomas E. Satteethwaite, M.D., Microscopist to St. Luke's 
Hospital (N.Y., U.S.A.). 
Plates CLVI. and CLVII. 
DuKiNa the last few years a great deal of attention and study has 
been directed toward a somewhat remarkable group of substances 
that enter largely into the composition of the body, where they 
form, in union with one another, a connected system, and so have 
obtained for themselves the name connective substances, their office 
being to furnish support or protection for the vessels, nerves, 
muscles, or epithelial bodies. 
One or more of these substances may be found in every tissue 
or organ, where they are deeply concerned in all changes, such as 
those of repair, degeneration,, or disease. The evident importance 
of knowing the characters of these substances in their various 
modifications has attracted to them a great deal of study, but 
opinions are still somewhat divided about them, there being little 
definite agreement as to the structure they exhibit even in the 
healthy and adult condition. 
It has therefore been difficult in all cases to decide how much 
the modified appearances they present have been the result of 
altered action, or merely variations that belong to the natural life 
of the substance. 
The determination of what constitutes the normal condition is, 
then, a matter of the first importance, and it is in this direction 
that the present inquiries have been made. The present essay is 
designed to embody a series of experimental researches upon the 
general subject of connective substances, with the view of deter- 
mining some of the more important facts that have been matters of 
controversy. 
The name connective substances has been adopted because it is 
already in use by leading histologists, and because it is an ex- 
tremely convenient word under which to group together a large 
number of animal substances that have a very close relation with 
one another. The name was first proposed by Eeichert in 1845, 
and embraces bone, cartilage, dentine, and the delicate forms called 
mucous tissue, adenoid tissue, neuroglia, fat tissue, fibrillated con- 
nective tissue (fibrous tissue), intermuscular tissue, corneal tissue, 
tendon tissue, and elastic tissue. 
The general reasons for classifying these substances separately 
may be stated as follows : They are all said to be derived from the 
middle germinal layer of the embryo ; * one form in one animal is 
* The sustentacular tissue of the brain and cord is thought to be an exception 
to this. Frey's 'Histology,' p. 196. 
