434 
ON HOCK LAMENESS. 
Recueil, and another has occurred to him lately, in which the 
posterior mediastinum was doubled by thick, false, organized 
membranes, which gave to this partition a thickness and a power 
of resistance that effectually prevented it from rupture. 
These cases, however, he considered as exceptions to a general 
rule ; nevertheless, they somewhat contradict the assertion of his 
confrere, that “ the operation of paracentesis on one side of the 
thorax would effectually empty both sacs of their contents.” 
In conclusion, we ought always, by auscultation and percus- 
sion on both sides of the thorax, to ascertain the existence of 
effusion on both sides, and the necessity of puncture on both 
sides. 
Rec. de Med. Vet., Fevrier 1837. 
[This is a most interesting and important subject, and we 
earnestly invite our correspondents to the consideration of 
it.— Y.] 
Since translating the above, we have been reminded that Pro- 
fessor Rigot discovered a similar structure of the mediastinum 
of the horse in 1825-6. It is contained in the Recueil of June 
1827. The following is the account of it : — “ M. Rigot has 
discovered an anatomical structure in a great number of horses, 
which, according to him, explains the serious nature of hy- 
drothorax in the horse. It consists of a communication be- 
tween the two pleural sacs, by means of little apertures in 
the posterior (the great) mediastinum, separated by filaments, 
and giving to that membrane the appearance of a piece of 
gauze.” 
ON HOCK LAMENESS. 
By Professor Dick, Veterinary College, Edinburgh. 
In your last Number I read a letter from Mr. Spooner, of 
Southampton, in which he describes what appears to him to be 
the cause of many cases of obscure hock lameness, and accuses 
veterinarians generally because they have not before noticed his 
papers upon the same subject. I have, therefore, with some 
degree of reluctance, been induced to offer a few remarks upon 
the subject, which would not, however, have been made had it 
not been for the kind of challenge given. I read the first case 
he gave with some degree of surprise, but allowed it to pass, 
thinking some one else would have noticed it ; and feeling that 
any remarks from a nominal Editor might have interfered with 
