66 , MANUAL OF PHYSIOLOGY. 



tion must be warded off by a degree of cold that checks its chem- 

 ical activity. 



If the chemical integrity of protoplasm be destroyed and its 

 death produced, many new substances appear, among which are 

 representatives of each of the great chemical groups found in the 

 animal tissues. Thus, besides water and inorganic salts we get 

 from protoplasm carbohydrates represented by glycogen, lecithin, 

 and other fats, and several albuminous bodies, which will be de- 

 scribed in the groups to which they belong. In addition to these, 

 protoplasm often contains some foreign bodies which have come 

 from without, and special ingredients of its own manufacture, such 

 as oil, pigment, starch, and chlorophyll. 



Blood plasma. There is also a body in living blood which must 

 be included in this group, as it undoubtedly has a much more 

 complex constitution than any of the individual albuminous 

 bodies, presently to be described, which can be obtained from it. 

 This is proved by the following facts : first, its death is accompa- 

 nied by a series of chemical changes, viz., disappearance of free 

 oxygen, diminution of alkalinity, and a rise in temperature; and 

 second, that several albuminous bodies appear which were not 

 present as such in the living plasma. 



The spontaneous decomposition of separated blood plasma may 

 be delayed by cold; at freezing point the chemical processes are 

 thus held in check. During life the exalted constitution of the 

 plasma is sustained by certain chemical interchanges which go on 

 between it and its surroundings. This question will be more fully 

 discussed when the coagulation of the blood is described. 



Muscle plasma. Likewise, as will be found in the chapter on 

 Muscles, there exists in the soft, contractile part of striated mus- 

 cles a plasma which at its death spontaneously breaks up into 

 several distinct albuminous bodies and forms a coagulum. These 

 changes are accompanied by acidity of reaction, the disappearance 

 of oxygen and an elevation of temperature, showing that distinct 

 chemical change is taking place. 



Oxyhcemoglobin, the coloring matter of the blood, should be 

 included here among the important chemical bodies more com- 

 plex than the albumins. This singular body can be broken up 



