8 June, 1907.] Elements of A/riiiial PJiysiology. 34i 



an organ \vhich remains in its normal condition but from which the blood 

 supply has been cut off. The probable reason for this strange occurrence 

 is that during starvation the body has to live on itself, that is, has to 

 digest its own substance as food, and that cutting an organ away from 

 the circulation is onlv an extreme form of star\ation. 



CLASSIFICATION OF THE MORE IMPORTANT ENZYMES FOUND IN THE ANIMAL 



BODY. 



a. Those that act on carbohydrates — 



Invertase which changes cane-sugar into dextrose and levulose. 

 Maltase which changes maltose into dextrose. 

 Lactase which changes lactose into dextrose and galactose. 

 Diastase which changes starch, glvcogen and dextrin into 

 maltose. 



b. Those acting on proteins — ■ 



Trypsin which changes protein into amino acids. 



Pepsin (in conjunction with an acid) which changes protein into 



proteoses. 

 Erepsin which changes proicoses into amino acids. 



c. Those acting on fats — 



Lipase which changes fats into glycerine and fatty acids. 

 (/. Those which accelerate the oxidation of substances — 



Oxidases, probablv manv in number, and each fitted for the 

 oxidation of a particular substance. 



e. Those which produce clotting — 



Thrombin (called also fibrin-ferment) which changes soluble 

 fibrinogen in the blood into the clot fibrin. 



Rennin (called also lab) which transforms soluble caseinogen 

 into the curd casein. 



CHAPTER Vn. 



Muscle. 



Muscle we mav regard as the tissue which is responsible for all 

 intrinsic movements in the higher animals whether of the body as a 

 whole (running, swimming, jumping, &c.) or of individual parts of the 

 body (circulation of the blood, movements of eyes jaws stomach &c.). 

 As has been alreadv stated, the essential elements of muscle are cells 

 in which contractilit\ is highlv specialised. All muscle-cells are longer 

 than they are broad and when thev contract the length is diminished 

 whilst the breadth is increased. The change is therefore one of shape 

 and not of size. 



Skeletal Muscle. 



The subdivision of muscle into three classes has alreadv been given. 

 The first class which is called striped, voluntary or skeletal muscle, and 

 which is familiar to us as the flesh of an animal, possesses certain char- 

 acters already implied in these names. Such muscle on microscopic 

 examination is seen to consist of cells which are striped horizontally, the 

 stripes being due to rows of little prismatic bodies which by their change 

 of shape determine the total change of shape in the cell. The second 



