96 
PROGRESS OF MICROSCOPICAL SCIENCE. 
more than groups of these plasma-cells. The author ascribes to this 
category : 1. The cells of the so-called interstitial substance of the 
testicle ; 2. The cells of the hypophysis cerebri ; 3. The cells of the 
carotid gland ; 4. Large round cells, which are found not unfre- 
queutly as an adventitious covering on the vessels of the brain ; 
5. The cells of the suprarenal capsules ; 6. The cells of the corpus 
luteum; 7. The so-called decidua or serotina cells of the placenta. 
It is characteristic of these cells that they always appear arranged 
directly around the blood-vessels, which they cover as with sheaths. 
The author proposes the name of "perivascular cellular tissue" for them. 
The Microscopic Structure of Tendon. — A paper by Herr Dr. Herzog 
is published in the ' Zeitschrift fiir Anat. und Entwickelung,' &c.,* 
which is thus abstracted by Dr. Thin in a communication to the 
' Medical Kecord ' (June 1876). Dr. Herzog examined transverse 
sections of the frozen tendo Achillis of the calf. The well-known 
stellate spaces and their connecting lines (so-called connective-tissue 
corpusles) appeared dark. The tendon substance enclosed within 
these spaces and lines, designated by the author a primary bundle, 
was divided into a number of fields, separated from each other by 
clear anastomosing lines. In these fields the fibrillaB were seen as 
dark points. The author succeeded in filling the stellate spaces and 
their connecting lines with an injection mass, the result being a com- 
plete blue network. Upon this Dr. Thin himself observes that the 
drawing of these peculiar " fields" reminds one at once of Cohnheim's 
fields in sections of frozen muscle. He believes them to represent 
transverse sections of the structures he has lately described in tendon 
as primary bundles (seen lengthways), not to be confounded with the 
primary bundles of Herzog, which he termed secondary bundles. 
Musical Sand examined beneath the Microscope. — A paper on this 
subject, which is really a somewhat curious one, is published in 
the last number, of the ' Proceed, of Califor. Acad, of Sciences ' 
(vol. v.). Mr. Frink states that " in order to ascertain, if possible, the 
^. cause of the sound that is produced by the sand from Kauai, presented 
to the Academy at a former meeting, I investigated its structure under 
the microscope, and I think the facts I have ascertained fully explain 
the manner in which the sound is produced. As the grains of sand, 
although small, are quite opaque, it was necessary to prepare them so 
that they should be sufficiently transparent to render their structure 
visible. This was effected by fastening them to a glass slide and 
grinding them down until one flat surface was obtained. This surface 
was then attached to another slide, and the original slide being 
removed, the sand was again ground down until sufficiently transpa- 
rent. The grains were found to be chiefly composed of small portions 
of coral and apparently calcareous sponges, and presented under the 
microscope a most interesting object. They were all more or less 
perforated with small holes, in some instances forming tubes, but 
mostly terminating in blind cavities, which were frequently enlarged 
in the interior of the grains, communicating with the surface by a 
* Band i. Heft 3 and 4. 
