PLASMATA. 65 



CLASS A. NITROGENOUS. 

 Group I. PLASMATA. 



Under this group may be placed a great variety of materials 

 which must be acknowledged to exist in the living tissues as 

 exalted chemical compounds, of whose chemical constitution, how- 

 ever, we are ignorant, since it is altered by the death of the 

 tissue. 



There are some exceedingly unstable associations of albuminous 

 bodies with other substances, and they at once break up into their 

 more stable constituents, dead albumins, fats, salts, etc., as soon 

 as they are deprived of the opportunities of chemical interchange 

 and assimilation which are necessary for their life. 



Although we can only theorize as to the real chemical consti- 

 tution of such substances, we must believe that they really exist 

 in the living tissues as chemical compounds, and, moreover, as 

 chemical compounds endowed with special properties which impart 

 the specific activity of their textures, whose molecular motions in 

 fact are the essence of the life of the tissues. 



Protoplasm. By far the m.ost widely spread and important of 

 these is the soft, jelly-like substance, Protoplasm. This is the 

 really active part of growing textures of all organisms, whether 

 animal or vegetable, and forms the entire mass of those interme- 

 diate forms of life, the protista, which are now generally regarded 

 as the original fountain head of life on the globe. 



This material commonly exists in small independent masses 

 (cells), in which we can watch all the manifestations of life, assim- 

 ilation, growth, motion, etc., taking place. We must assume that 

 this substance is a definite chemical compound ; and, further, since 

 the living phenomena are exhibited only so long as it preserves 

 its chemical integrity, we may conclude that its manifestations of 

 life depend upon thesustentation of a special chemical equilibrium. 

 Not only is this equilibrium destroyed by any attempt to ascertain 

 the chemical composition of protoplasm by analysis, but even for 

 its preservation the protoplasm must be surrounded by those cir- 

 cumstances which are known to be necessary for life, viz., moisture, 

 warmth, and suitable nutritive material, or its chemical destruc- 

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