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PROCEEDINGS OF SOCIETIES. 
diabetes. Mr. Needham had observed the same changes in the brain 
in cases of hydrophobia, and in cases of heart disease where there 
had been much congestion. The President thought the changes 
described not uncommon ; they were mentioned long ago by a French 
writer as owing to wasting of the brain in old age, and lately by 
Dr. Lockhart Clarke in paralysis of the insane. These appearances 
may not be pathognomic ; and Dr. Dickenson could not find them in 
the parts of the brain which when injured cause a diabetic condition ; 
they are found too iu seemingly healthy brains. His first-described 
perivascular spaces are by some considered lymphatic ; but may 
they not be the tunica adventitia of the artery separated, and under 
diseased conditions filled with blood or inflammatory material ? 
In the case given it was not likely they were owing to simple me- 
chanical distension of the vessel, for, if so, why should the vessel not 
remain distended ? it would scarcely again collapse. They were more 
easily explained by wasting of the brain substance, and consequent 
filling of the perivascular spaces — whether tunica adventitia or not — 
with serum, since a vacuum cannot exist, and this wasting a severe 
illness or bad feeding might bring about. 
Dr. Greenfield had always observed a catarrhal condition of the 
central canal of the cord in cases of convulsions, and what the Presi- 
dent described as tunica adventitia he thought an additional struc- 
ture to help support the vessel. 
Dr. Coupland in reply stated he had in preparing the spinal cord 
prepared it first for twenty-four hours in spirit and water, and then 
in weak chromic acid. He did not know if the child were badly 
nourished, nor how long it had been ill. 
TJrate of Soda in the Heart. — Mr. Ward exhibited a specimen 
where in a gouty subject the coronary artery was found plugged, the 
plug containing acicular crystals of urate of soda. Death was sudden, 
from rupture of left ventricle ; the heart substance was friable. 
The President had seen sudden death in cases of plugging of the 
coronary artery. Dr. Greenfield stated that fatty change in the heart 
was said to follow plugging of the coronary arteries : he had not 
observed it uniformly. He quoted Dr. Quain’s cases of plugged 
coronary artery ; in all death was from ruptured heart. 
Mr. Golding Bird asked if any chemical test had been applied to 
the crystals. He had once succeeded in obtaining under the micro- 
scope, by the addition of weak acid, crystals of uric acid from the 
acicular crystals of urate of soda contained in a section of “ gouty ” 
cartilage. 
Mr. Ward, in reply, had not applied any chemical test ; the heart 
substance was not fatty, and he did not know which coronary artery 
was plugged. The crystals did not polarize. 
Blood-crystals of Bat, exhibited by Dr. Pritchard, were obtained 
after killing the animal with aether ; a drop of the blood with water 
is placed on a glass slide and covered at once ; on coagulation the 
crystals are seen in the spaces between the fibrin. If cemented thus 
they keep a long time, being “ in vacuo.” 
Myxoma . — A specimen exhibited by the President, in which the 
