148 ADVENTITIOUS PRODUCTS IN THE 
thus formed exactly resemble those represented, with the ex¬ 
ception of the fibrous sheath, which in the choroid plexus was 
absent. These are, in many respects, very similar to the mineral 
concretions so common in the prostate gland.” 
It is to be regretted that we are not acquainted more fully 
with the symptoms which such morbid products occasion during 
life. However, it would appear from the case described by Mr. 
Percivall, in the Number of The VETERINARIAN for December 
1851, that they may occasionally produce serious results, and 
be efficient predisposing causes to apoplexy, inasmuch as the 
pathognomonic signs of this affection were exhibited by the 
mare both before and at the time of death. Mr. Percivall adds, 
that “ the mare was a ‘ weaver’ in her stall, and was known 
to be of that nervous temperament to cause her to be, without 
warning, dangerous of approach.” Might not this peculiar 
habit of weaving originate, in this as in other instances, from the 
morbid deposits being so intimately related with structures 
vitally important 1 
Since the above remarks have been penned, Mr. Percivall 
has kindly given me the plexuses he removed from the brain of 
the same. 
The two tumours, either of them about the size of a nut, are 
such as are frequently found in brains of old horses: they are 
red conglomerate masses, irregularly papillated and covered by 
a dense fibrous sheath; gritty and tough under the knife. The 
fluid which may be squeezed from them consists principally of 
cholesterin, masses of earthy matter, dissolving with effer¬ 
vescence in hydrochloric acid, and giving as residue some 
amorphously arranged organic matter, mostly modified states of 
the unsaponifiable fat. A portion of the tumour washed in 
ether becomes extremely brittle and hard; a drop of the solu¬ 
tion, if allowed to evaporate, deposits granular matter, and 
bodies such as delineated at fig. 2. The greater part of this 
precipitate resists the action of liquor potassae, so that the 
objects alluded to are probably crystalline forms of cholesterin, 
the result of rapid deposition. To ascertain this I dissolved 
some biliary calculi in boiling alcohol, allowed this to cool, 
and washed the residue with proof spirit, when the same 
phenomenon manifested itself. Professor Muller, on dissolving 
cholesteatoma in boiling alcohol and ether, found that it yielded 
a residuum bearing the following characters : “ No oil remained, 
but a finely granular fat, probably stearine. To these granular 
masses were attached very delicate elongated microscopic la¬ 
mellae of unequal size, slightly bent, and closely resembling the 
lanceolate leaves of plants. Their edges are convex, and, con¬ 
verging, meet to form the pointed extremities of the lamellae. 
