1896 - 97 .] Dr T. H. Milroy on Nucleins and Paranucleins. 257 
From some ( e.g ., ichthyulin of the carp’s eggs) a cupric oxide 
reducing body has been obtained, while in the case of others it is 
absent (casein, ovovitellin). 
Just as a nuclein is a combination between nucleic acid and 
albumen, so a paranuclein may be regarded as a combination 
between paranucleic acid and albumin. 
Unfortunately, we know very little about the acid constituent of 
the paranucleins. That of the paranuclein of casein has been 
referred to by Clara Willdenow, Salkowski, and Hahn, though it 
has never been properly described. Before I refer to the acid 
constituent of the paranuclein of ovovitellin, it is necessary for 
me to describe another acid which was formerly regarded as pos- 
sibly identical with the paranucleic acid of the paranucleins. 
When a solution of nucleic acid in water is heated for a short 
time on a water bath, the nucleic acid is split up into nuclein 
bases, another base called cytosin, and a phosphorus-holding acid 
— thymic acid. This acid — thymic acid — still retains the proteid 
precipitating power of the nucleic acid, and is richer in phosphorus 
than the latter. From analyses which Kossel has made of it, the 
atomic proportions of nitrogen to phosphorus are as 1*5:1, or, 
according to some of my own, 1 *6 : 1 ; while in all nucleic acids 
the proportions are always as 3:1. 
This acid does not give on decomposition nuclein bases, agreeing 
thus with the acid constituent of the paranucleins. What is the 
nature of these precipitates which thymic acid causes in syntonin 
solutions'? Are they at all comparable with the natural para- 
nucleins ? These bodies I have examined, and shall shortly sum up 
some of their principal characters. They do not possess so high a 
percentage of phosphorus as the nucleins, owing to the fact that 
thymic acid precipitates a greater excess of loosely combined 
syntonin than nucleic acid does ; therefore, on digestion with 
pepsin, the percentage of phosphorus gradually rises, showing that 
the excess of syntonin is slowly removed. I may take as an 
example of many analyses the following : — 
Percentage of phosphorus before peptic digestion, . 2*755 
After 6 hours’ digestion, ..... 3*286 
>> 
16 
18 
. 5 045 
. 4*34 
>> 
