GLOSSARY 303 



Mutations — sudden variations appearing in individuals of one 



species and capable of transmission to their descendants. 

 Mycetozoa or Myxomycetes — protozoa with naked protoplasm 



occurring on damp surfaces in the form of jelly-like masses, 



living on organic debris, auioebiform without mycelium but 



later plant-like. 

 Myeloplax — a multinucleated cell occurring in the marrow of 



bones. 

 Nematodes — a class of worms with thread-like body, mouth and 



intestinal canal, including the parasitic thread-worms, &c. 

 Neuroglia — cells in the nervous system which correspond to the 



connective- tissue cells in other organs. 

 Nitrification — the transformation of salts of ammonia (chiefly the 



sulphate and the carbonate) into nitrites and nitrates under the 



influence of the nitrifying bacteria. 

 Plasma — the fluid portion of the blood freed from the red and 



white corpuscles which float in it : it contains fibrinogen but, 



not having been allowed to coagulate, no fibrin {vide Fibrin). 

 Proteins — substances resembling egg-white and containing nitrogen, 



carbon, oxygen, hydrogen, and sulphur. 

 Ptomaines — products of putrefaction, some of them poisonous, 



isolated from putrefying organic matter (first discovered in 



dead bodies). 

 Putrefaction — the decomposition of protein substances by microbes 



and their ferments with the production of gas, foul smells, and 



sometimes poisonous substances : as a result of putrefaction 



organic matter is restored to the state of inorganic elements. 

 Septic — derived from o-en-o-is — corruption and applied to material 



which can produce or undergo bacterial infection, e.g., a septic 



wound, a septic instrument, a septic dressing. Hence the 



words " antiseptic," a substance acting against this action, and 

 t " aseptic," the absence of sepsis. In modem surgery antisepsis 



has given place to asepsis. 

 Serum— the clear fluid expressed from the clot of coagulated blood : 



it represents the fluid portion of the blood minus the cells and 



minus the fibrin which forms the clot [vide Fibrin). 

 Stereochemical— the chemistry of matter may be treated as 



depending on arrangements of the atom in space in the 



molecule i^ide isomeric). 

 Sucrase — sugar-splitting ferment. 

 Symbiosis — the living together of dissimilar organisms each 



dependent on the other : the best examples are the lichens 



where a fungus and an alga live together. 

 Urease — urea-splitting ferment : producing ammonia from the 



urea, the main nitrogenous constituent of urine. 

 Vagus — the nerve supplying the heart, lungs, and stomach. 

 Vitalism — the modern application is to a theory which postulates, 



at least provisionally, some other activity in the life processes 



