83 



CONSTITUTION OF THE SECRETING VILLI. 



All the secreting papillae and villi are said to be constituted 

 very nearly alike, and to consist essentially of a double mem" 

 brane, basement and epithelial, with a layer of fine areolated 

 tissue between them both, the inner and outer surface of which 

 is covered by minute villi, so called from the surfaces they 

 cover resembling velvet, or plush. In each villus or papilla, a 

 plexus or little knot of arteries, veins and nerves are found to 

 exist, by which the processes of accretion, of elaboration, and 

 secretion, are carried on. The exact modus operandi of these 

 operations, however, are so complex and difficult to investigate, 

 that they have not yet been fully understood or satisfactorily 

 explained. 



THE FLUID ELEMENTS OF THE FOOT. 



i. Blood. 



2. Marrow. 



3. Lymph. 



4. Synovia. 



5. Mucus. 



6. Substances undergoing transformation into horny tissues. 



7. The perspiratory fluid. 



PHYSICAL PROPERTIES OF THE BLOOD. 



The first, only, of these elements, the blood, demand any 

 special mention beyond that which might have been made when 

 considering the secreting structures, and the enumeration 

 which was necessary to present a complete account of the sub- 

 stances that play their part in the complex organism designated 

 the foot of the horse. 



IMPORTANT PHYSIOLOGICAL FACTS. 



Anything like a full consideration of the properties and con- 

 stitution of the blood would carry me further into the domain 

 of physiology than the majority of my readers would be dis- 

 posed to follow me. There is, however, one view of its physi- 



