MR. MAYHEW ON PHYSIOLOGY OF THE HEART. 269 
artery, and that they cannot move in the opposite direction 
after they reach their level position.* It is this circumstance 
that gives rise to the production of the second sound of the 
heart, which is quite ignored by Mr. Mayhew. That sound 
is caused by the falling down of the blood upon, and the 
consequent tension of, the semilunar valves, and could not be 
produced at all if the valves were as Mr. Mayhew thinks, 
i( merely floating membranes.” That the second sound is so 
produced, has been satisfactorily and clearly proved by the 
well-known and conclusive experiments made by Dr. C. J. 
B. Williams and Dr. Hope, and recorded in Dr. Williams’ 
work on the f Pathology of the Chest,’ published in 1835. 
The following are two of these experiments : — 
“ Observation YI. A common dissecting hook was passed 
into the pulmonary artery (of an ass), and was made to draw 
back, and thus prevent the closure of the semilunar valves ; 
the second sound was evidently weakened, and a hissing 
murmur accompanied it. A shoemaker’s curved awl was 
then passed into the aorta, so as to act in the same way on 
the aortic valves. The second sound now entirely ceased, 
and was replaced by a hissing. 
“ Observation VII. The hook and awl were withdrawn ; 
'the second sound returned, and the hissing ceased.” 
These experiments require no comment ; but I must hasten 
to a conclusion. As a whole, Mr. Mayhew’s paper is badly 
arranged, illogical, and sometimes, indeed, hardly intelligible. 
It contains many errors, of which I have pointed out the 
more important and serious. It enunciates opinions unsup- 
ported by any evidence whatever, and often entirely disproved 
by observation. Such opinions could hardly have been ad- 
vanced with credit twenty years ago, and still less at the 
present time, when the tide of progress flows fast. I have, 
therefore, felt myself justified in pointing out their fallacy, in 
order that the veterinary profession, as a whole, may not 
appear to lag far behind in anatomical and physiological 
knowledge. 
Edinburgh Veterinary College ; 
April 17, 1854. 
* The views herein stated are admirably expressed by Mr. Struthers, in 
a paper read before the Physiological Society, in June, 1853, and now pub- 
lished in a collection of that gentleman’s works, entitled ‘Anatomical and 
Physiological Observations.’ (Edinb. 1854.) 
XXVII. 
3C) 
