THE THYROID GLAND. , 585 



considerable. In recent preparations it is obvious that the air-cells 

 communicate in many ways, and in any case, that they are not merely 

 terminal on the extremities of the branchiae. If it be desired to investi- 

 gate the whole subject, inflated and dried lungs (it is better in an 

 inflated lung to tie off an end and dry it by itself), or corroded prepara- 

 tions, or lungs injected with uncolored substances (wax and resin) are 

 most suitable, and with such, a definite result will be obtained, after a 

 series of observations. 



Before the injection of the bronchice is proceeded with, the air must 

 be exhausted in the air-pump, for which purpose, also, though less con- 

 veniently, a well-fitted syringe may be employed. The injection of the 

 bloodvessels is readily effected and the preparations should be kept 

 wet; sometimes, when injected with opaque material, sometimes, follow- 

 ing the processes of Schroder and Halting, with transparent substances 

 (Prussian blue, &c.), dried preparations are to be preferred. The air- 

 cells and bronchia?, the larynx and trachea, are readily examined. The 

 epithelium of the air-cells is obtained in large quantity in every section 

 through the lung, as well as ciliated cells. If it be wished to study the 

 alveoli, the air must previously be carefully removed. These are best 

 displayed in Man, in whom, also, all the other parts, such as cartilage, 

 elastic elements, muscles, and glands, are easily obtainable. 



Literature. M. Malpighi, "De pulmonibus epistolse II adBorellum." 

 Bonon. 1661; F. D. Reisseisen, " Ueber den Bau der Lungen, eine 

 gekrbnte Preisschrift," Berlin, 1822; [Magendie, " Mdm sur la struc- 

 ture du poumon, in < Journ. de Phys. exper. ;' " Rainey, " On the minute 

 structure of the lungs," Philosoph. Transact. 1845;] J. Moleschott, "De 

 Malpighianis pulmonurn vesiculis," Heidi. 1845, Diss. and, " Ueber die 

 letzten Endigungen der feinsten Bronchien," in the Hollandischen 

 Beitragen, I. p. 7 ; Rossignol, " Recherches sur la structure intime du 

 Poumon, Brux.," 1846; A. Adrian!, "De subtiliori pulrnonum struc- 

 tura." Trajecti ad Rhen. 1847, Diss.; Kostlin, " Zur normalem und 

 patholog. Anatomic der Lungen," in Gries. " Archiv," 1848, Heft. IV. 

 p. 282, and 1849, Heft II. p. 167 ; E. Schultz, " Disquisitiones de struc- 

 tura et textura canalium aeriferorum," cum tab., DorpatiLiv. 1850. 

 Dissert. 



OF THE THYROID GLAND. 



180. The thyroid gland, or body (glandula thyroidea), is a so-termed 

 " ductless gland," which in its external aspect much resembles the race- 

 mose glands, seeing that its round, closed gland-vesicles, ^-oV of a ^ ne 

 in size, are surrounded by a fibrous stroma and subdivided into rounded 

 or elongated, often slightly polygonal lobules, J-J of a line in size, 

 the gland- granules of authors ; and these again are associated into 

 larger, though not completely separated, lobes, out of which the main 



