THE ORIGIN AND NATURE OF FAT. 
591 
further to demonstrate that adipose tissue is independent of 
connective tissue, he refers to the characters and relations of 
fat in the Batrachia. The masses of fat that surround the 
uro-genital apparatus of these animals in the larval state 
consist of large, round, transparent nucleated cells, not sepa- 
rated by any intervening substance except blood-vessels. 
Passing to the Mammalia (says the Lancet , from which we 
quote), he points out that the first formation of fat in the 
embryo occurs round the kidneys, and thence gradually ex- 
tends into the connective tissue of the mesentery after birth. 
He considers a strong argument in favour of the indepen- 
dency of the adipose tissue to be the fact that it always has, 
down to its smallest lobules, its own proper and closed system 
of blood-vessels, which, it is curious to observe, very closely 
resembles that of the acinous glands. These researches of 
Toldt enable us to explain the absence of fat in regions 
where everything appears to favour its formation, as in the 
sub-muscular connective tissue of the intestinal canal. It 
explains also the persistence of the tissue, with its charac- 
teristic features, even when all the oily matter has been re- 
moved by absorption. Whilst fully concurring in the general 
statement that fat-cells possess in mature adipose tissue a 
distinct membrane, he differs from Czajewicz in maintaining 
that when first formed they are destitute of a membrane, this 
only becoming visible in the later embryonal periods. The 
minute masses of protoplasm they contain, however, remain 
throughout life. He makes an interesting observation to 
the effect that spring frogs that have fasted through the 
winter, and are excessively lean, present fat drops in which 
no membrane is distinguishable, but which, reduced to their 
protoplasmic primary mass, possess the powder of amoeboid 
movements. From the consideration of these facts, M. 
Toldt has arrived at the conclusion that the protoplasm of 
the fat-cells, when supplied with sufficient nutriment, is ca- 
pable, like a gland-cell, of forming fat as a kind of secretion ; 
and, inversely, wdien the consumption of oxidizable material 
exceeds the supply, it possesses the power of using up the 
stored-up fat and discharging it into the blood. The mode 
in w hich fat is laid up has also been investigated by Fleischer, 
wfith a view of determining whether, in accordance with 
Liebig's idea, the amylaceous compounds ingested are con- 
verted into fat directly ; or whether, as Yoit thinks, the fat 
consumed in the economy is derived from the fat of the food, 
and that the amylaceous compounds are only serviceable as 
readily combustible compounds, by means of which the fat 
developed from albuminous compounds, and already present 
