MEDEARIS AND MARBLE: THYMUS GLAND. 125 



thoracic region of the body were stripped of skin, and the thymus 

 beneath (easily seen) dissected away from the surrounding tissue. 

 The gland was then washed, dried superficially on filter paper, and 

 weighed. This process was carried out on almost 150 pigs, and 

 tables and curves were made and studied to determine tendencies. 



RELIABILITY OF RESULTS. 



Before going into the body of the report it may be well to con- 

 sider just how reliable were the results obtained, and wherein lay 

 sources of error. (1) In the weighing of the pigs, some of them may 

 have absorbed more of the formaldehyde preservative than others; 

 some may have lost more of their body fluids than others. This 

 error seems to us, however, as negligible. (2) The chemical bal- 

 ances used were not of the best, and, too, thethymi may not have 

 received exactly the same treatment after removal from the pig, 

 although every effort was put forth to secure uniformity. To this 

 end, all weighings (practically) were made by one operator. (3) 

 Lengths of the pigs may not be entirely accurate, although here, too, 

 the greatest care possible was taken to secure exactness. (4) Lastly, 

 incomplete removal of the thymus, or removal of other tissue as 

 thymus, may have occurred in some cases. The greatness of this 

 error depends, of course, upon the skill of the workers, and it is 

 their hope that this has been a negligible factor of error. Taking 

 all in all, then, it is extremely probable that the material and data 

 to be set forth are accurate to this degree, that they may be taken 

 as the basis for conclusions of a definite nature. Such conclusions 

 are, in our minds, accurate and reliable enough to merit considera- 

 tion. 



THE THYMUS: ITS GENERAL SHAPE AND EXTENT. 



It was not our purpose to study the structure of the thymus in 

 any detail, and this part of the report is merely made in passing, 

 without any attempt at thoroughness. Our findings seem to be 

 similar in many respects to those of Badertscher (3) as to the 

 anatomy of the gland.^ In the fcetal pig -it is comparatively very 

 long, extending usually from a point over the upper half or third 

 of the heart, underneath the sternum (as viewed from the ventral 

 side), and up to the base of the mandible. The portion covering 

 the heart is strongly attached to the pericardium ; it is roughly tri- 

 angular in shape, with the apex pointing posteriorly, and lies mainly 

 to the left of the median line. The anterior end of this, the thoracic 



1. In a further paper (7) Badertscher discusses the development of the thymus in the pig 

 from the standpoint of histogenesis. 



