THORACIC FASCIA. 527 



pressed out, which has a whitish color, and coagulates upon the 

 addition of alcohol. 



Although it is called a gland, no excretory duct has ever been 

 found connected with it. 



The thymus gland in the foetus at birth, extends from the 

 fourth rib, as high up as the thyroid gland. It rests upon the 

 pericardium below, and is separated from the arch of the aorta 

 and the great vessels, by a fascia, called by Sir A. Cooper; the 

 thoracic, which is composed of a dense layer of fibre-cellular 

 membrane, stretched between the concave margins of the first 

 rib of each side so as to pass horizontally across the upper open- 



Fig. 130 * 



ing of the thorax. It is connected below with the fibrous sac of 

 the pericardium, with the arch of the aorta which it in a measure 

 sustains and the great vessels that come off from it. Above, 

 it is connected with the sheath of the carotid, and the deep 

 cervical and tracheal fasciae. This fascia has an opening in 



* A section of the thymus gland at the eighth month, showing its anatomy. 

 This figure is taken from one of Sir Astley Cooper's beautiful engravings. 1. 

 The cervical portions of the gland. The independence of the two lateral glands 

 is well marked. 2. Secretory cells seen upon the cut surface of the section ; 

 these are observed in all parts of the section. 3, 3. The pores or openings of 

 the secrelory cells and pouches ; they are seen covering the whole internal 

 surface of the great central cavity or reservoir. The continuity of the reservoir 

 in the lower or thoracic portion of the gland, with the cervical portion, is seen, 

 in the figure. 



