102 Rivero and Boussingault on the Milk of the Cow-Tree. 
liquoFj in which are found the two principles already men-^ 
tinned. 
It is almost impossible to filtrate the milk : the liquor which 
passes is, however, sufficiently limpid. We have already said, 
that alcohol gives a slight precipitate, and then it may be fil- 
trated. 
The liquor has a dark colour ; it slightly reddens blue paper ; 
when concentrated, it does not, by cooling, deposit crystals ; 
when evaporated to the consistence of jelly, and treated by alcohol 
at 40°, a little sugar is dissolved. The remaining mass has a 
bitter taste. Dissolved in water, the solution still reddens blue 
paper. Ammonia forms a precipitate sufficiently abundant. This 
character, added to the bitter taste, made us suspect the pre- 
sence of a salt of magnesia. Our conjecture was verified, by 
putting a drop of this solution upon' a plate of glass, with, a 
little phosphate of ammonia, then mixing the two liquids with 
a glass-tube, and forming a letter, the character remained ad- 
hering to the glass in the most palpable manner. By this ingeni- 
ous process, for which we are indebted to Dr Wollaston, the pre- 
sence of one or tv/o hundred parts of magnesia may be detected. 
We had now to determine the nature of the acid combined 
with the magnesia. We thought it was acetic acid ; but sulphu- 
ric acid did not disengage any odour of vinegar, and only car- 
bonised the salt of magnesia. We are still ignorant of the nature 
of the acid, but we suppose it is not acetic acid. 
The matter upon the filter, when dried, assumes the appear- 
ance of unrefined wax, and when heated, it exhales the smell of 
roasted milk: it is wax mixed with fibrin. 
There results from the preceding experiments that the milk of 
the cow-tree contains, 
1. Wax, 4. A salt of magnesia, not the acetate, 
2. Fibrin. 5. A colouring matter. 
3. A little sugar. 
It contains no albumen, nor curd, nor catechu. 
getable albumen has to animal albumen. M. Vauquelin has detected, in the ve- 
getable juice of the Carica papaya, a principle which has also a great similitude 
with animal fibrin, (Thomson, t. iv. ch. 1. of Fibrins, page 87). Recently we 
have examined the fresh juice of Carica papaya, and we have found in it the sub- 
stance mentioned by the celebrated French chemist ; it appears to be similar to 
that of the milk of the cow-tree. 
