Answers to Queries. 178} 
tion is the expression of a general condition indicating the 
diminution of water in the tissues ; or it may be to excess of saline 
matters in the blood. Salt increases consumption of water, and 
this in turn increases the transformation of nitrogen in the body. 
If an animal be deprived of salt, nutrition is interfered with ; 
deprival of common salt causes albuminuria. The salts, alkaline, 
serve to neutralise the suJphuric acid formed by the oxidation of 
the sulphur of the proteids. Salt plays a most prominent part in 
connection with the diffusion of fluids through membranes, and its 
presence is necessary for the solution of the globulins. V. A. L. 
331.—Canada Balsam.—The advantages of using solutions of 
Canada balsam are, the facility and cleanliness of working, the ease 
with which air is expelled, and the opportunity of mounting objects 
in balsam which will not bear the slightest degree of heat. The best 
solvents are chloroform and benzole. Turpentine may be used, 
but does not give such a clear solution. An opacity occurring in 
liquid balsam mounts is generally due to moisture in the object, 
and may often be removed by gently warming the slide. 
jj; Ae rloce: 
330.—Lobster.—If B. O. B. will read Dr. A. B. Griffiths’s 
article in Science Gossi~, pp. 57, vol. 22, 1886, on “The green 
gland of Astacus fluviatilis” (Cray-fish), he will find it very similar 
to the lobster, and will be able to understand the subject. See also 
Huxley’s “ Cray-fish,” pp. 83 and 224, etc., Int. Science series. 
Ve Aw: 
334.—Octopus.—Yes, the octopus ( Cephalopoda) possesses odon- 
tophores or tongue-ribbons, the hinder part of which is furnished 
with recurved spines. See “Invertebrata,” by Huxley, and Zoology 
by Claus and Sedgswick, or any Zoology. VEAL es 
337.—Drawing on Glass.—Grind lamp-black with gum water, 
and some common salt. Draw the design with a pen or hair 
pencil. We AC IE: 
337.—Etching on Glass.—The objects to be etched are 
immersed ina bath of melted wax, which on removal forms a 
thin coating over their surface. On this the designs are carefully 
scratched out by means of a pointed instrument, which removes 
the wax along the lines of the pattern. The glass is then 
immersed in a solution of hydrofluoric acid, contained in a leaden 
vessel. ‘The acid, which is very corrosive, attacks all the portions 
of the glass not protected by the wax, thus eating out the lines of 
the engraving on the glass. When this is done, all that remains is 
to clear away the wax. Owing to the destructive nature of 
hydrofluoric acid, a special room is kept, in which it is applied, the 
