284 SANTE NACCARATI 



rounded body, easily recognized by its pink color, across the 

 adipose tissue and suprapericardial connective tissue, larger or 

 smaller than a pea according to the size of the animal. 



In the classic treatise of Bojanus (1819-21) in which are 

 reported with clearness and precision all the characteristics 

 of the macroscopic anatomy of Emys europea, the thyreoid is 

 taken for the thymus. The latter, when it exists, is a long double 

 organ of a light gray color, located in front of the carotids, with 

 which it is in close contact, at the point of conjunction of the 

 neck with the thorax. It is strange that so able an anatomist 

 should have fallen into such an error. The pink color of the 

 thyreoid is due to the blood which it contains, the amount of 

 which is very considerable (according to Tschuovsky, 560 cc. of 

 blood pass each minute through 100 grams of human thyreoid 

 tissue). When the excess of blood in the thyreoid of the tortoise 

 is eliminated, it acquires the appearance of an opalescent lens. 



Volume and weight. The volume and weight of the thyreoids 

 of Emys europaea are very variable. The most noteworthy 

 variations are due to the size and age of the animal. With the 

 purpose of establishing as exactly as possible the average weight, 

 I have weighed the thyreoid of thirty Emys and found that in 

 adults weighing about 275 gm. the thyreoid has an average 

 weight of 0.025 gm. In general, 100 gm. of body weight corre- 

 sponds to about 10 mgm. of thyreoid. For man this proportion is 

 about five times as big. If the weight of the Emys is taken with- 

 out its carapace and plastron, which averages about 40 per cent 

 of the total, according to my measurements of thirty animals, 

 the proportion is 16 mgm. of thyreoid to 100 gm. of the animal's 

 weight. There are great individual variations from the average. 

 In another paper I have prepared, in tabulated form, the weights 

 of the thyreoid and other glands in groups of several species of 

 reptiles, including Emys europaea. 



As regards the volume of the thyreoid in Emys europaea, what 

 I have said regarding the weight holds good, namely, that it 

 varies within very wide hmits, according to the size of the animal. 

 In general it may be stated that in an animal of 300 gm. weight, 

 the maximum diameter of the gland is about 5 mm. 



