THE THYMUS GLAND. 141 



tionately in early infancy, particularly its pyramidal process, 

 possibly the duct may be obliterated when the gland begins to 

 be restrained in its growth ; but, if this were the case, the duct 

 ought to have been found during the period indicated. TJje 

 probability is, that it is a diverticulum of blood from the saliva- 

 ry glands daring the intermittence of their action; and from 

 the marked sympathy between it and the brain in goitre, it 

 may exercise a corresponding function on this organ during 

 its intervals of repose. 



Duverney* has described a small azygous muscle on the 

 middle line of the body, coming from the under margin of the 

 base of the os hyoides, and running over the middle of the thy- 

 roid cartilage, to be inserted into the upper margin of the isth- 

 mus of the thyroid gland. Scemmering calls it Levator Glan- 

 dule Thyroidea?, and speaks of it as being found more frequently 

 on the left side, and about half of the breadth of the thyreo- 

 hyoideus. After many special examinations for it I have found 

 it in but few instances; I, therefore, consider it rare; though 

 without a close attention to structure, the pyramidal process 

 of the isthmus of thp gland may, fmm the similitude of colour 

 and position, be very readily mistaken for it, which I have rea- 

 son to believe has been frequently the case.f Some few fibres 

 are often found going to the isthmus of the gland from the cri- 

 co-thyroid, and the thyreo-hyoid muscles, or from the thyroid 

 cartilage. 



* 



SECT. III. OF THE THYMUS GLAND. 



This body (Glandula Thymus) is placed between the trachea 

 and the upper extremity of the sternum. It is irregularly tri- 

 angular, its broadest part being above, and the narrower below. 

 In the adult, it is in a collapsed and shrivelled state, and 

 scarcely presents a vestige of what it once was; it is, there- 

 fore, only in the infant that it can be satisfactorily studied. 



* Essai D' Anatomic en tableux imprimes, pi, IV. Paris, 1745. 



f The unassisted eye, in a strong light, is generally sufficient to determine the 

 structure; but in case of doubt, by boiling the gland, if there be muscular fibres 

 along this process, their longitudinal and parallel direction will become evident; 

 they also may then be torn asunder, so as to be made still more distinct ; where* 

 as, the vesicular structure of the gland is not susceptible of division into fibres. 



