Baxterin, their Nature and j Function. 
373 
albuminous matter it is which forms the protoplasm of its cells, this 
albuminous matter it is which serves as nitrogenous food for animals; 
these again supplying the food for other animals and man. In the 
living body of these the albuminous matter becomes broken up, 
yielding nitrogenous principles like urea and allied substances, 
which again, after further oxidation in the soil and in water, serve 
to supply nitrates to the plant. Also, the bodies of animals and 
plants after death form a large stock from which by a long chain of 
processes, induced and sustained by micro-organisms, lower nitro- 
genous compounds, and ultimately ammonia and nitrates, are pro- 
duced, from which the living plants principally draw their nitrogen. 
From this it is evident that the vegetable kingdom is dependent 
for its nitrogen chiefly on processes by which from the albumin of 
dead organic matter, by the activity of micro-organisms, in the first 
place lower nitrogenous principles and ultimately ammonia, and in 
the second place, also by micro-organisms, nitrites and nitrates are 
formed. Now, the micro-organisms which are capable of producing 
the first series of decompositions of dead albuminous matter form, 
so to speak, the first army of attack ; it is this army which, while 
multiplying at the expense of albumin, decomposes it, and thereby 
is instrumental in changing it into lower nitrogenous principles, such 
as leucin, tyrosin, indol, and ammonia. Amongst the large number 
of species of putrefactive bacteria I will describe two only, which 
by their wide distribution may be considered as playing a very 
important part in this decomposition of albumin. The first is the 
species known as Proteus vulgaris , the second is the Bacillus coli. 
(a) Proteus vulgaris.— This species is the common putrefactive 
organism ; it is almost invariably present in dead and decaying 
albuminous matter ; it is the organism which in dead animals and 
man plays the principal part in the destruction and resolution of 
the body ; it is present in the cavity of the normal intestine ; it is 
found in connexion with effete and dead matter occurring in the 
body in health and disease ; it has a wide distribution in nature, 
and is present wherever organic matter happens to be in a state of 
putrescence ; it is liable to pass from this and to be transmitted to 
other putrescible matter by air currents, by dust, by water, by 
human contact or otherwise, and then to set up in this new organic 
matter the same state of putrescence. The same applies to the 
Bacillus coli , which has also a very wide distribution, and which 
is in most instances associated with putrefaction and decomposition 
of albuminous matter ; it is a normal inhabitant of the human and 
animal intestine, and from here often passes into the soil, water, 
and air. 
These two species of organisms may be considered, then, as being 
of great importance in the destruction and resolution of putrescible 
matter — in short, of dead albuminous matter. Both these species 
are motile bacilli. 
Proteus vulgaris, as its name implies, presents itself in forms so 
varied, that it is at first sight difficult to recognise them as belonging 
to one and the same species : coccus forms, short ovals, short and 
