298 
spaces are true canals limited on the outside by the 
adventitia, on the inner side by the vascular wall. He 
has arrived at this opinion by investigations conducted 
on the vessels of fresh brain substance, as well as on 
specimens hardened in osmic acid, and in bichromate of 
potassium. His results were also confirmed by injected pre- 
parations, made by injecting a solution of Prussian blue 
under yery gentle pressure into the subarachnoid spaces ; 
which not only filled very beautifully the meningeal peri- 
vascular spaces, but penetrated into the cortical part of the 
brain along the vessels, and along the inner, not the outer, 
wall of the lymphatic sheaths. 
The size of these channels was found to vary with the age 
of the individual, the particular part of the brain, and the 
diameter of the adjacent vessel. They are, on the average, 
wider in children than in adults; and larger in the cerebral 
hemispheres than in any other part of the brain. From more 
than a thousand measurements the author finds the average 
diameter to be—in adults 62u;' in children 70u. The 
following table shows the average diameters in different parts 
of the brain : 
ADULTS. CHILDREN. 
Cerebral hemispheres. : 99ip (a : 81 
Corpora striata , : y 77 : , 75 
Thalami optici ‘ . , 76 ; : 54 
Cerebellum. , : : 56 
Pons varolii_ . ; ; , 38 
Very careful comparative measurements also established 
the fact that the lymphatics are not filled from the adjacent 
vessels, but that their distension holds a converse relation to 
the fulness of the blood vessels. Hence in rapid hyperemia 
of the brain the lymphatics are compressed ; when the blood- 
pressure diminishes they dilate, and so on. These relations 
were well illustrated by measurements taken from brains in 
several morbid states ; all those in which there was hyper- 
eemia showing the lymphatics small, while in anemia they 
were larger. 
Many interesting details are given respecting pathological 
conditions of the lymphatics, which we cannot further enter 
into. 
Researches on the Normal and Pathological Anatomy of the 
Frog’s Skin—By Carl Jos. Eberth, Professor of Pathological 
Anatomy in Zurich ; with three plates (Untersuchungen, &c. 
Engelmann, Leipzig). 
Professor Eberth’s researches were made on Rana escu- 
1 » = one thousandth of a millimétre. 
