74 Transactions Texas Academy of Science. — - 1908 - 1909 . 
as containing many isomers of albumin, a bright light is shed upon 
the obscure process of nutrition. 
“You ask whether a substrate totally destroyed may be regen- 
erated. I do not believe it can, since the destruction would involve 
the patterns or moulds by means of which new molecules are manu- 
factured from the furnished products of food digested. Besides, re- 
cent investigations show that the substrate of an enzymic reaction 
is never totally destroyed ; that the reacta are arrested by the end prod- 
ucts (specific antibodies) before all the subtrate is hydrolized. This 
matter was not discussed in the paper you read, but is gone into 
a more recent paper (my address as President of the Texas 
Academy of Science). I there offer evidence in proof that the end 
products of an enzymic reaction, which arrests the process before it 
is completed, also changes the remaining substrate into isomers, and 
thus destroy its vulnerability to the pathogen. This process is called 
the 1 convertability of enzymic reactions,’ and I think it satisfac- 
torily explains the cause of lasting immunity. I must refer to my 
address for details with regard to the effect on the organism that 
may result from total destruction of one of the many groups of 
Albumin isomers of the serum, I do not believe it would be serious, 
but don’t know. As a matter of fact there appear to be many in- 
dividuals and some races who are naturally immune to certain in- 
fections. Now, according to my hypothesis, natural immunity is 
largely due to absence of susceptible groups of substrates.” 
One of the most fruitful periods of Dr. McLaughlin’s life was 
passed during the time he was Professor of the Practice of Medicine 
in the Medical Department of the University of Texas. I have 
received a long and appreciative letter from Dr. John T. Moore, who 
was his assistant during a large portion of that time, and from it 
I take the liberty of quoting freely, paraphrasing some parts of the 
letter in order not unduly to extend the time of this address. 
On assuming the duties of the chair, Dr. McLaughlin saw at once 
the necessity of bringing the laboratory work of the students into 
closer connection with the teaching in the hospital wards. Pre- 
viously the laboratory had been in a building at a distance from the 
hospital. Towards this great improvement in methods he labored 
earnestly and enthusiastically, but with his usual unselfish and modest 
methods. For a time he and his assistant fitted up a room in the 
basement of the hospital, with simple apparatus, at their own ex- 
pense, and it was only after bearing this burden for some years that 
the Regents of the University were able to provide funds for the 
equipment of a satisfactory laboratory. Dr. McLaughlin’s method 
