142 Progress of Foreign Science. 
Memoir on the Milk of the Cow Tree (Palo de Vaca). By J.B. 
Boussingault and Mariano de Rivero. 
Among the astonishing vegetable productions that are met with 
at every step in the equinoctial regions, a tree is found which yields 
in abundance a milky juice comparable in its properties to the 
milk of animals, and which is employed for the same purposes, as 
M. de Humboldt witnessed at the farm of Barbula (Cordillere lit- 
torale de Venezuela), where he drank some of the milky juice. 
The tree grows in considerable numbers on the mountains which 
command Periquito, situated to the north-west of Maracay, a 
village to the west of the Caraccas. The vegetable milk pos- 
sesses the same physical properties as that of the cow, with the 
single difference, that it is a little viscid. It has the same taste. 
In its chemical properties, it differs sensibly from animal milk. 
It mixes with water in all proportions, and when thus diluted, it 
does not coagulate by ebullition, The acids do not convert it into 
clots, as happens to cow’s milk. Ammonia, instead of causing a 
precipitate, renders it more liquid. This character indicates the 
absence of caoutchouc. Alcohol occasions a feeble coagulation, 
or rather renders the juice more easy of filtration, The recent 
juice slightly reddens litmus. Its boiling temperature is the same 
as thatof water. Exposed to heat, it exhibits at first the same 
phenomena as cow’s milk. A pellicle is formed at its surface, 
which prevents the disengagement of aqueous vapours. On re- 
moving the successive pellicles, and evaporating it at a gentle 
heat, an extract is obtained resembling frangipane; when the 
action of heat is longer continued, oily drops are formed, which 
increase according as the water is carried off, and finally afford an 
oily liquid, in which a fibrous matter floats which becomes dry 
and horny, as the temperature of the oil is raised. Then is dif- 
fused the best characteristic odour of meat frying in grease. By 
the action of heat, therefore, the vegetable milk is separable into 
two parts, the one fusible and of a fat nature, the other fibrous and 
of an animal nature. If the evaporation of the vegetable milk is 
not pushed too far, and if the fusible matter be not raised to ebul- 
lition, it may be obtained without alteration. It then possesses 
the following properties :— 
It is of a white slightly yellowish colour, translucid, solid, and 
resists the impression of the finger. It begins to melt at 40° 
centig., and when the fusion is completed, the thermometer indi- 
cates 60°.. Alcohol of 40° (sp. gr. 0°817) dissolves it totally by 
ebullition, and it precipitates on cooling. It saponifies with eaus- 
tic potash, and with ammonia forms a soapy emulsion. Nitric 
acid heated on it, dissolves and converts it into oxalic acid. It 
resembles refined bees’ wax, and serves for making candles. The 
fibrous substance is procured by decanting the melted waxy 
