298 



MORPHOLOGICAL STUDY OF TRACHEAL AND BRONCHIAL CARTILAGES. 



when this is present it serves to intensify the density. A modification of the circular 

 cartilage is seen in figure 24, where a spur from one of the ends of the cartilage is 

 associated with a second and smaller bronchus. The cartilage itself is shown in 

 figure 25. 



In the lobus inferior of each lung the common type of cartilage in the angle 

 between the main stem bronchus and its larger branches is the saddle-shaped car- 

 tilage (fig. 11); branches of the third and fourth order may have associated with 

 them any one of the other types of cartilage. 



When the smaller bronchioles are reached and the last trace of cartilage 

 appears, it is not in the form of a thin plate, but as a short rod-shaped cartilage 

 placed, as a rule, lengthwise along the bronchiole. This has been found to be the 

 case, not only in the animals usually studied in the laboratory, but also in man. 



In sections, a piece of cartilage is frequently found superimposed over one or 

 more pieces of cartilage; this is due to the contraction of the trachea, or the bronchus, 

 or to the plane of the section. Often pieces of different cartilages appear in a trans- 

 verse section of the trachea or of a bronchus (fig. 2), giving the appearance of a 

 series of plates arranged about its lumen ; the preceding study, however, shows that 

 they are integral parts of cartilage which have a definite form. 



From the anatomical standpoint the act of respiration seems to be even more 

 complex than the usual description. This morphological study of the cartilages 

 shows that they constitute a mechanism for maintaining the normal position or 

 capacity of the lung, and that a critical study of this mechanism (that is, the stress 

 and strain to which it is subjected) is desirable. Associated with this is the relation 

 of the bronchial musculature to the cartilages, especial!}" at the point where bronchi 

 divide. A study of the musculature at the carina tracheae has convinced the author 

 that it is by no means easily accomplished, though quite necessary for a complete 

 understanding of the bronchial architecture. 



LITERATURE. 



CUVIER, G., 1805. Logons d'anatomie comparee. Paris. 

 HELLER, R., and H. v. SCHROTTER, 1S97. Die Carina 



trachea 1 . Ein Beitrag zur Kenntnis der Bifurka- 



tion der Luftrohre, nebst vergleichend-anato- 



mischen Bemerkungen iiber den Bau derselben. 



Denkschr. Akad. Wiss. Wien, math.-nat. Kl., 



Bd. 64. Wien. 

 HENLE, J., 1879. Handbuch der systematischen anato- 



mie des Menschen. Braunschweig. 

 HORNER, W. E., 1839. A treatise on special and general 



anatomy. Philadelphia. 

 KING, J., 1840. On the forms of the cartilages which 



keep open the principal divisions of the bronchial 



tubes. Guy's Hospital Report. 

 LUSCHKA, H., 1869. Die Anatomic des Menschen. 



Tubingen. 



MILLER, W. S., 1904. The carina trachea 1 of the domes- 

 tic cat (Felis domcsticus) . Anat. Anz. Bd. 25. 

 , 1913. The trachealis muscle: its arrangement at 

 the carina trachese and its probable influence on 

 the lodgment of the foreign bodies in the right 

 bronchus and lung. Anatom. Record, vol. 7. 



NARATH, A., 1901. Der Bronchialbaum der Saugetiere 

 und des Menschen. Bibliotheca medica. Abt. A. 

 Anatomie, Heft 3. 



OWEN, R., 1S6S. On the Anatomy of vertebrates. Lon- 

 don. 



SCHAFER, E. A., 1912. Text-book of microscopic anat- 

 omy. Quain's Anatomy, vol. 2, Pt. 1. 



WATERS, A. T. H., 1860. The anatomy of the human 

 lung. London. 



