6 
Transactions Texas Academy of Science. — 1907. 
definite alterations in physiological processes inevitably produced the 
same pathological changes. „ 
Thus hepatic congestion and “nutmeg liver” occur with mathematical 
certainty as the result of valvular disease of the heart, when the leak- 
ing valves act so imperfectly as to allow the pressure from the con- 
tracting heart muscles to pass backwards into the venous system: and, 
again, cardiac hypertrophy will follow as a physical necessity, when 
it is necessary to raise vascular tension to a point sufficiently high to 
enable a chronically inflamed kidney to excrete a proper quantity of 
urine. 
By degrees, the pathologist became a physicist, a physiologist, a chem- 
ist, and an anatomist rolled into one; or, to speak more correctly, men 
who possessed special training in these directions inevitably drifted into 
pathology. 
Although new pathology has made immense strides, we are still at 
the very threshold of knowledge. Yet work of such marvelous accuracy 
is being accomplished in every branch, and particularly at the present 
time in the problems concerned with metabolism, that the future is 
full of hope. 
It is generally conceded that physiological activity is the result of 
chemical action; and that life ends at the exact moment when chemical 
action ceases in the animal cell. Therefore, it must be held dogmatic- 
ally that all animal energy is derived from chemical sources. These 
chemical processes are of necessity very complex, and 'at the present 
time we are able to formulate them approximately only. Thus we know 
that by hydration proteids are changed into peptones, and that the 
reversal of the process, viz., dehydration, results in the reformation of 
proteids. Yet the constitution of proteids is so complex that chemical 
formulae to represent the changes that occur during metabolism can 
only represent the processes in a very incomplete manner. 
As will be shown later on when dealing with the action of the toxins 
and antitoxins on the proteid matter of animal protoplasm, our knowl- 
edge is more limited still, and to enable us to express even the most 
primitive ideas of their chemical combinations, we make use of fantastic 
formulas and still more fantastic diagrams. 
In the lowest forms of animal life we find the anatomical structure 
of the simplest possible nature, yet adequate to carry on all necessary 
physiological functions. Thus, in the amoeba, respiration, digestion, 
reproduction, and locomotion are all carried on by a simple unicellular 
organism. As we ascend the animal series, we find in the simpler multi- 
cellular forms, a special adaptation of certain cells to perform particular 
functions; as in the hydra, where arrangement exists similar to that 
of the three primitive layers of the embryo of a highly developed animal, 
