626 VERTEBRATED ANIMALS. 



termination of each air-tube in man, is not less than 18,000 ; 

 and that the total numher in the entire lungs is six hundred 

 millions. 



439. The following list of the parts of the bodies of Yerte- 



brata, of which Injected pre- 



FlG - 333 - parations are most interesting 



as Microscopic objects, may 

 be of service to those who 

 may be inclined to apply 

 themselves to their produc- 

 tion. Alimentary Canal; 

 Stomach, showing the orifices 

 of the gastric follicles, and 

 the rudimentary villi near the 

 pylorus ; Small Intestine, 

 showing the villi and the 

 orifices of the follicles of 

 Lieberkiihn, and at its lower 



Arrangement of the Capillaries of the air-cells of ^ Qr f f>, o Potrovinn rrleinrlc! 

 the Human Lung. P ait tlie Cyeiiail glands , 



Large Intestine, showing the 



various glandular follicles: Respiratory Organs; Lungs of 

 Mammals, Birds, and Eeptiles ; Gills and Swimming-bladder of 

 Fish: G-landular Organs; Liver, Gall-bladder, Kidney, Paro- 

 tid: Generative Organs; Oviduct of Bird and Frog; Mamma- 

 lian Placenta ; Uterine and Foetal Cotyledons of Ruminants : 

 Organs of Sense; Iris, Choroid, and Ciliary processes of Eye, 

 Pupillary Membrane of foetus ; Papillae of Tongue ; Mucous 

 Membrane of Nose; Papillae of Skin of finger: Tegumentary 

 Organs ; Skin of different parts, hairy and smooth, with vertical 

 sections showing the vessels of the Hair-follicles, Sebaceous 



lands, and Papillae; Matrix of nails, hoofs, &c. : Tissues; 

 'ibrous, Muscular, Adipose, Sheath of Tendon. 



440. Development. The study of the Embryological develop- 

 ment of Yertebrated animals has been pursued of late years 

 with great zeal and success by the assistance of the Microscope; 

 but as this is a department of inquiry which needs for its suc- 

 cessful pursuit a thoroughly scientific culture, and is only likely 

 to be taken up by a professed Physiologist, no good purpose 

 seems likely to be served by here giving such an imperfect out- 

 line of the process, as could alone be introduced into a work 

 like the present; and the reader who may desire information 

 upon it, will find no difficulty in obtaining this through systema- 

 tic treatises on Physiology. 1 



1 The Author takes the liberty of referring to his " Principles of Comparative Physio- 

 logy," 4th Ed. chap, xi, as containing a general view of the whole subject, with refer- 

 ences to the principal sources of more detailed information. 



