SECTION XXI 



ANIMALS AND ANIMAL GLANDS 

 AND SECRETIONS 



Organotherapy, or the treatment of disease by means of animal 

 secreting organs or of preparations derived from them, has been con- 

 tinually in use for some 5,000 years, but it has recently been scienti- 

 fically studied and considerably extended. Before proceeding to this 

 section of the work it will be desirable to take a very brief survey of 

 the animal kingdom, more especially as several animal substances 

 have already been described. 



Various systems of zoological classification have been from time 

 to time proposed, but the following one is readily intelligible and 

 well adapted for the object in view. By it the animal kingdom is 

 divided successively into Phyla, Classes, Orders, Families, Genera, 

 and Species. The following outline embraces the chief Phyla, Classes, 

 and Orders, and indicates their most important characters. 



Phylum I. Protozoa. This phylum includes the simplest and 

 most primitive animals, each consisting of a minute, single cell. 

 Loose colonies are sometimes formed by division or budding, but 

 differentiated tissues are not developed. Most of them live in water, 

 and some form calcareous or siliceous skeletons. They are grouped 

 into three classes, viz. the Rhizopoda, which are predominantly 

 amoeboid, the Sporozoa, which are usually encysted, and the Infusoria, 

 which are actively motile by means of cilia or flagella. The Rhizo- 

 poda include such animals as the Foraminifera, the accumulated 

 calcareous skeletons of which form most chalks and limestones. 

 The Sporozoa are mostly parasitic, e.g. the malarial parasite. The 

 Infusoria move actively and are found in great numbers in stagnant 

 water, vegetable infusions, &c. 



Phylum II. Porifera. These are mostly passive, vegetative, 

 marine animals which form colonies and exhibit slight division of 

 labour, sexuality, &c. Familiar examples are the ordinary sponges 

 in which very minute pores on the surface (inhalant canals) lead 

 into chambers lined with flagellated cells. The movement of the 

 flagella draws a current of water with food particles through the 





