524 
POPULAE SCIENCE EEVIEW. 
we give our readers a few of Ms results or conclusions. The following is his 
table of the diet required by several classes : — 
Subsistence 
Diet. 
Diet in 
Quietude. 
Diet of 
Adult u» full 
health. 
Diet of 
active 
Labourers. 
Diet of 
Hard- 
worked 
Labourers. 
ozs. 
ozs. 
ozs. 
ozs. 
ozs. 
Plesh-formers... 
2-0 
2-5 
4.2 
5-5 
6-5 
Fat 
0-5 
1-0 
1-8 
2-5 
2-5 
Starch 
12-0 
12-0 
18-7 
20-0 
20-0 
Starch equiva- 
lents (as heat 
producers) ... 
13-2 
14*4 
22-0 
26-0 
26*0 
Carbon 
6-7 
7-4 
11-9 
13*7 
14-3 
With regard to the exact value of the two orders of food, Dr. Playfair con- 
siders that Liebig is amply justified in viewing the non-nitrogenous portions 
of food as mere heat-givers. They never can act vicariously for albuminous 
bodies as tissue formers, although tissues may and do evolve heat by trans-' 
formation when required to do so. That heat-givers do operate indirectly on 
the waste of tissues cannot be questioned. They facilitate transformation by 
keepiug up animal heat, and by the promotion of the circulation. Cold- 
blooded reptiles become more active when warmth is supplied to them, and 
conversely, warm-blooded animals become more sluggish when the heat of 
their bodies faU, as during hibernation. “ Such dependencies of different 
groups of food, acting co-ordinately, are incessantly found ; but, nevertheless, 
each group has its own specific work to perform.” 
New Method of Examining Nervous Tissue. — M. Eoudanovsky suggests 
the following mode of preparing specimens of nervous structure : — 
(1.) Prepare with Yalentin’s knife sections of the nervous tissue frozen at 
a temperature of from 10° to 15° Reaumur. (2.) Colour them by means of 
infusion of cochineal or carmine. (3.) Cover the pieces with Canada balsam, 
or a mixture of glycerine and isinglass. Although we do not see anything 
very strikingly novel in M. Roudanovsky’s method, we nevertheless give some 
of the results of his observations : — 
(1.) An examination of a transverse section of a nerve shows that the 
primitive element of the nerve is a tube with a pentagonal or hexagonal 
outline. 
(2.) The walls of the nerve-tubes, which are composed of connective tissue, 
form a perfect net-work. 
(3.) The wall-forming tissue gives rise to cavities, or reservoirs, by which 
the nutrient fluid is conveyed. 
(4.) The isolated appearance of nervous tubes is an artificial phenomenon. 
(5.) The axis-cylinders are coloured by the cochineal as well as the walls of 
the tubes ; the former appear as knotted fibres in the centre of the tubes. 
The writer m the Microscopical Journal, in commenting upon the above 
statements, considers that the method adopted by M. Roudanovsky probably 
