SECT. 179.] INVESTIGATION OF THE LUNGS. 39 1 



fig. 7). Iii the growth of the foetus, these granules become more 

 and more numerous with the multiplication of the bronchial rami- 

 fications ; and in the fifth month they touch each other, and form 

 small lobules, of o"i^" to 0'48'" in diameter, each of which has 

 probably arisen from a single gland-granule, or bronchial termin- 

 ation of the second month. These small lobules at first corre- 

 spond to the secondary lobules of the perfect lung ; the primary or 

 ultimate lobules with the air-vesicles themselves are produced by a 

 process of budding from the glaud-granule. The ultimate alveoli 

 an* first seen in the sixth month of foetal life, and new alveoli 

 are continually being added up to the period of birth (see my 

 Micr. A /tat., ii. 2, p. 323). In newly-born infants, the secondary 

 lobules measure 2"', 3'" to 4'", and the alveoli o - 03"', before they 

 are rilled with air; after the first inspiration, they increase to 

 °' 35"> 0'04"' to o # o6'" in diameter. The alveoli appear to be of 

 the same number in the infant as the adult, and the further en- 

 largement of the lungs seems to take place only by the progressive 

 growth of all their parts. 



The investigation of the lungs should present difficulty only with regard to 

 one point, viz., the relation of the pulmonary cells to the termination of the 

 bronchia ; but the difficulties here are really very considerable. In fresh pre- 

 parations, the air-cells are seen to communicate very freely, and they are 

 found at the ends of the bronchia in lateral groups, and not terminally only. 

 If it be desired to investigate the relation thoroughly, we make use of lungs 

 inflated and dried (it is better to tie off one end of an inflated lung and dry 

 it separately). Preparations formed by corrosion after injection, or lungs 

 injected with a colourless material (as wax and turpentine), must also be 

 examined ; and in all these ways together, we shall arrive at some definite 

 result. 



Before injecting the bronchi, the air must be drawn out by an air-pump, or 

 a well-acting syringe may be employed, although less adapted for this purpose. 

 The injection of the blood-vessels is not attended with any difficulty ; and 

 moist preparations, injected partly with some opaque substance, partly with 

 transparent materials (the process of Schroder and Harting), such as Prussian 

 blue, are to be preferred to dried preparations. The air-cells themselves, the 

 bronchi, the larynx, and trachea, can be easily examined. The epithelium of 

 the pulmonary vesicles, and also ciliated cells, are obtained isolated in large 

 quantities in every section through the lung. If it be desired to study the 

 alveoli, the air must previously be carefully removed. They are most beau- 

 tiful in man, in whom, also, all the other parts, as the cartilages, elastic 

 elements, muscular fibres, and glands, are readily accessible. 



Literature. — M. Malpighi, Do Puhnonibus Epistola? II ad Borellum, Bonon., 

 1661. F. D. Reisseisen, Ueber den Ban d< r Lungen Bine gekrbnte Preisscforift, 

 Berlin, 1S22. J. Moleschott, De Mcdpighianis Pulmonum Vesicidis, Heidelb., 

 1 8+5, Diss., and Ueber die letzten Endigungen derfeinsten Bronchien, in the Hoi- 



