60 OSKAK KLOTZ 



the level of the pole. It is loosely connected with the thyroid capsule, and 

 at times is found to lie outwardly displaced or in a downward direction, 

 opposite the midportion of the lobe. Less commonly, the superior para- 

 thyroids are removed at some distance above the pole of the thyroid in the 

 vicinity of the thyroid cartilage. 



The inferior parathyroids are less fixed in their relation to the lobes of 

 the thyroid. Usually found at the posterior and outer margins of the lobe 

 and close to the tip, they are often displaced downwards, so as to lose con- 

 tact with the thyroid and lie along the loose tissue near the carotid sheath 

 (Schaper). Again, their position along the trachea may make it difficult 

 to distinguish the glandules from lymph nodes, or scattered remains of 

 thymus tissue. The close points of origin of the thymus and the inferior 

 parathyroids, not uncommonly bring these structures into anomalous rela- 

 tion with each other. Thus, the inferior parathyroids, or accessory gland- 

 ules to them, may bo found within thymus tissue (Thompson, Verebely, 

 Erdheiin) and the reverse has also been observed in which the thymus 

 tissue was found incorporated in the parathyroids. 



Variations in Animals. The parathyroids of lower animals are still 

 less constant in their position than in man, this is particularly true of the 

 inferior parathyroids, of the dog as well as the cat (Harvier and Morel), 

 monkey (Vincent and Jolly) and rat (Erdheim). The dislocation of the 

 lower parathyroids, or their accessory structures into the thymus is more 

 often seen than in man, while the implantation of them into the structure 

 of the thyroid is so frequent as to suggest for this a normal position. This 

 intrathyroid glandule is identified with difficulty, and in the dog requires 

 particular attention. In color and general appearance, the tissue may dif- 

 fer but little from that of the surrounding thyroid, while the demarcation 

 of the two structures by the presence of a capsule may be all but wanting. 

 MacCallum never found the human parathyroids imbedded in the thyroid 

 gland as is not uncommonly seen in dogs, Thompson and Leighton ob- 

 served a most irregular -distribution of the parathyroids in dogs, scattered 

 lobules of this tissue being found as far down as the bifurcation of the 

 trachea. This is in agreement with our own experience. Gley also com- 

 ments on the inconstancy of the position of the parathyroids, noting four- 

 teen variations in the situation of the glandules in thirty-three dogs. 

 Alquier found the parathyroids in their normal situation only nine times 

 in fourteen dogs. Because of this great variation in position, it is evident 

 that the greatest care must be exercised in drawing conclusions on experi- 

 ments which have dealt with only the parathyroids in their normal posi- 

 tion. 



Variations in Number in Man. The number of parathyroids also suf- 

 fers- variations to a considerable degree, and the symmetrical distribution 

 is far from constant. One glandule may be present alone on one side with 

 one, two or three irregularly arranged on the other. Accessory parathy- 



