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with the compressors of the rectum, pass round and are inserted on 
the inferior aspect of the sacs into a circular set of fibres which 
surround an uninvested space in the middle line, opposite the median 
dilatation. The round ligaments of the uterus end on this mus- 
cular tunic. The rectum is surrounded by a set of remarkably 
developed compressors. 
4. On the Thyroid Gland in the Cetacea ; with Observations 
on the Relations of the Thymus to the Thyroid in these 
and some other Mammals. By William Turner, M.B. 
(Lond.), Senior Demonstrator of Anatomy, University of 
Edinburgh. Communicated by Professor Goodsir. 
The author, in the first instance, directed attention to the dis- 
crepant statements of various comparative anatomists respect- 
ing the thyroid gland in the Cetacea, quoting from the writings of 
John Hunter, Meckel, Cuvier, Carus, and Dr Martyn. He then 
related the result of his own dissections made on three specimens of 
the common porpoise ( Phocccna communis ), one being a foetus, 
another a well grown male, the third an adult male. In each of 
these animals a well marked thyroid gland was found, lying on the 
anterior and lateral surfaces of the trachea at its upper end, and 
extending slightly upwards on each side over the outer surface of the 
cricoid cartilage. It presented no division into two lateral lobes, 
as described by Cuvier and Carus, but consisted of a single uniform 
mass extending across the middle line. In the adult animal, which 
was examined in the fresh state, the other specimens having been 
some time in spirits, the gland presented a dark purple tint, and a 
soft and somewhat succulent aspect. Both in the foetus and well 
grown animal, the thymus gland was exceedingly well developed. 
A detailed description of the position and relations of this gland was 
then given, the long ascending processes which pass upwards, by the 
side of the great vessels, as far as the thyroid gland, being especially 
pointed out. These processes were intimately connected with the 
lateral portions of the thyroid by cellular tissue, but were not con- 
tinuous with them. 
The author next referred to Mr Simon’s description of the thymus 
in the foetal dolphin. 
The microscopic characters of the thymus gland in the well- 
grown porpoise were then given. It was found to consist of small 
