258 SITUATION AND STRUCTURE 



responding with the structure of other glands), convinced Mr. 

 Hewson it must have an excretory duct ; yet possibly it might 

 be so small, or the coats so transparent, that when collapsed in 

 the dead body it might become almost invisible ; though during 

 life, while distended with the natural fluid, it might be more 

 readily perceived. Therefore the following experiments were 

 made in order to detect it. 



EXPERIMENT I. 



SECT. 30. The sternum of a half-grown dog being removed, 

 a ligature was passed round the thymus, including at the same 

 time all the neighbouring parts. The animal soon died. On 

 examining the parts contained within the ligature, no excretory 

 duct could be found ; but a great number of lymphatic vessels 

 made their appearance, filled with a darker coloured fluid than 

 ordinary. 1 



As the gland in this dog was small, it was suggested that the 

 experiment would probably succeed better in a larger animal, 

 which gave rise to the following experiments. 



EXPERIMENT II. 



SECT. 31. The chest of a calf being opened, a ligature was 

 passed round the lower part of the thymus, as had been done 

 in the former experiment, and the parts contained within the 

 ligature were taken out. On examining these very attentively, 

 a great number of lymphatic vessels, containing a fluid almost 

 similar to chyle, of a white colour, but not quite so opake, were 

 seen coming from every part of the gland ; one of which was 

 so large, that at first sight it had the appearance of an excretory 

 duct ; but on a more attentive examination, it was discovered 

 to be no other than a large lymphatic vessel. The remaining 

 parts were dissected with all possible care, but no excretory 

 duct could be seen. 



1 Ubinam is succus habitet, nondum consentitur. Ex thymi tamen exemplo, maximae 

 glandulae, crediderim, cum Nuckio, oinnino in areolis cellularum residere. Nam in 

 tota thymi glandula, ubicunque laeseris, exiguo etiam vulnere, in earn violationem ex- 

 primi potest, neque tamen aut manifesta cavitas reperitur, qua contineatur, neque ex 

 vase aliquo effluere videtur, cum et copia earn guttulam superet, quae ex vase non 

 magno inciso speretur, neque ex remotis giandulae partibus per vascula adeo facile in 

 vulnus urgeri posset, et denique manifesto cum spuma ex cellulis cavernulisque ex- 

 primatur. Hall. Elem. Phy. torn, i, p. 184. 



