PROGRESS OF MICROSCOPICAL SCIENCE. 
211 
developed from the free border of the five primary cells and a few of 
the other adjacent tall ones, but the exact manner in which the reticu- 
lation is formed has not been made out. The trabeculse are, like the 
rods, developed from the side of primary cells ; and although only 
three (on the outer side of the rods) persist in adult life, yet at birth 
numerous fine trabeculae are found to the inner side of the rods. He 
regards the merabrana tectoria as a secretion from part of the general 
epithelial layer ; it first appears as a thick but even layer, and as age 
advances that portion which covers the organ increases considerably 
in thickness. From the foregoing observations it will be seen that the 
rods, membrana reticularis, and trabeculae are developed from the 
walls of the original ej)ithelial cells, whereas the hair- and various 
other cells are formed from their contents ; and, lastly, that the mem- 
brana tectoria is a secretion from the same original epithelium. 
The method of preparation usually employed was as follows : 
The cochleee were always quite fresh. 
They were hardened in a ^ per cent, solution of chromic acid in 
ordinary methylated spirit ; ten days required. 
Decalcified in 1 per cent, solution of nitric acid in water. 
Transferred directly to gum-water, soaked a few hours, and then 
placed in a paper bag surrounded by spirit. 
Imbedded in Stirling's machine and cut. 
Gum gradually dissolved away in proof spirit. 
Mounted, stained or otherwise, in glycerine or Canada balsam. 
He has examined the cochleae of the following mammals : man, 
monkey, sheep, dog, cat, rat, guinea-pig, rabbit, porpoise, kangaroo. 
With the exception of the peculiarities in man and monkeys referred 
to, he has found a striking similarity in the organ of Corti of all these 
animals. 
Unfortunately all his efforts to procure the cochleae of a monotreme 
have as yet proved unsuccessful, a circumstance much to be regretted, 
as he fully anticipates that it presents some appearances which link 
the very dissimilar cochlece of mammals and birds. 
Microscopy at Philadelphia. — We have not yet received any report 
of the Exhibition ; but we believe Mr. Crouch and certain other 
makers are represented. In regard to microscopic specimens we have 
no doubt that this department has been well arranged, particularly if 
the authorities have placed the matter in the hands of Colonel Dr. 
Woodward. We learn that there are some four hundred frames 
which contain fungi of all kinds, many of them microscopic. 
The Dissection of Insects for examination of their Microscopic 
Anatomy. — Dr. Fripp, in an admirable paper on the subject of insect 
anatomy, gives the following account of the mode of going to work, 
which is of considerable interest to the practical observer.* He says : 
Much of our knowledge of internal structure has been gained by 
observation, under the microscope, of insects possessing a transparent 
integument. The larval forms are most suited for such examinations, 
and are best examined whilst living, when circulation or muscular 
* 'Proceedings of the Bristol Naturalists' Society,' vol. i., part 3. 
VOL. XVI. Q 
