532 



THE CELL AND MAMMALIAN HISTOLOGY 



coat similar to that of the gut. The bronchi have a ciUated 

 epithehum, and outside that there is elastic tissue, plain muscle, 

 and fibrous tissue, in that order. In the larger tubes the fibrous 

 tissue contains cartilage. It is the contraction of the muscle, 



dj. 



?.nu 



p.rru V. »•/• 



Fig. 414. — A transverse section of the spinal cord of a frog. 



c.c. Central canal ; d.f., dorsal fissure ; d.k., dorsal horn ; g.m., grey matter ; n.c, large nerve cell ; 

 p.m., pia mater ; v., vein ; v.j., ventral fissure ; v.h., ventral horn ; w.m., white matter. 



w.m. 



^£.7n. 



v.h. 





v.f. 



Fig. 415. — A transverse section of the spinal cord of man, taken through the 

 lumbar region, between nerves, with the pia mater removed. 



Lettering as in Fig. 414. 



which forms an irregular network, and of the elastic fibres, 

 which forces air out of the lung in the so-called passive expiration 

 of mammals. 



SPINAL CORD AND NERVES 



A section of the spinal cord (Fig. 415) shows that the nervous 

 tissue is surrounded by membranes or meninges. On the outside 



