460 SECTIONAL TRANSACTIONS.—M. 
experiments seem to show that: (1) The condition is produced in animals 
deprived of access to earth or other mixtures of minerals, and fed only on 
grains and certain other concentrates commonly used in pig-feeding. (2) The 
inorganic constituents in these feeding-stuffs do not correspond with the 
requirements of the growing pig. There is a marked deficiency of calcium 
and an excess of acid radicles. (3) If the mineral matter of a ration composed 
of these feeding-stuffs be adjusted to the requirements of the animal by a 
mixture of salts compounded to correct the deficiencies the disease does not 
occur. (4) The addition of Fat soluble A or of Water soluble C to a ration 
that produces the condition does not prevent the onset of the symptoms. 
It is believed that one, and probably the chief, factor in producing the 
condition is a deficiency in one or more of the necessary inorganic con- 
stituents of the food. 
19, Dr. J. B. Orr.—The Application of the Indirect Method of 
Caiorimetry to Ruminants. 
In recent years calorimetry has been practised on the human subject by 
various indirect methods. In the simplest of these methods a sample of expired 
air is collected in a bag by means of a mouthpiece with a two-way valve. From 
the volume of air expired in a given period, and the difference in the per- 
centage of O2 and of COQ, in the inspired and the expired air, the amount 
of Oz absorbed and of CO, exhaled during the period can be determined. 
oe .. Vol. of COzg exhaled ; E ‘ 
The ratio Vall of Ou absosbed? known as the Respiratory Quotient, gives 
an indication of the nature of the material oxidised. From the amount of 
oxygen absorbed the heat production can be calculated, since the consumption 
of any given amount of oxygen corresponds to the liberation of a definite 
amount of heat, the amount of heat per unit of volume of oxygen varying 
with the, Respiratory Quotient. 
For the application of the method to ruminants a special mask has been 
constructed. The mask fits over the muzzle, and is made airtight by a rubber 
band, which can be inflated. It is provided with two valves—an inlet and an 
outlet. From the outlet the expired air can be conveyed to and collected in 
a large bag. The volume of the air expired during the experimental period 
is determined by passing it through a gas-meter. The percentages of O,, CO,, 
and combustible gases in the expired air are determined by a modified Haldane’s 
gas analysis apparatus. 
From these results it is possible to calculate (a) the rate of formation 
of combustible gases; (b) the proportion of expired CO, which is due to 
fermentation in the rumen; (c) the heat production due to fermentation; and 
(d) the heat production due to tissue metabolism. Experiments which have 
been carried out by means of an airtight chamber have shown that CH, and 
COz are not lost through the skin or by the anus in amounts that seriously 
interfere with the accuracy of the results. Preliminary experiments have been 
carried out on the goat to determine the rate of metabolism of the animal (a) 
standing and lying, and (v) before and after feeding. 
Following this paper Mr. J. Golding exhibited photographs of an abnormal 
litter produced by a sow fed on a diet deficient in vitamin A. 
20. Major C. C. Hurst.—The Genetics of Egg Production in Poultry. — 
(Five years’ experimental breeding on Mendelian lines, from 1910-16, with 
three distinct utility strains of White Leghorns and White Wyandottes, show 
that the first year’s egg-production of a hen depends on the combined action 
of at least seven main genetic factors. The Mendelian pairs identified are :— 
E— e Early — Late Sexual maturity of pullets. 
W— ow Fast —Slow, - Rate of winter production. 
S— s Fast — Slow Rate of spring production. 
M— m Slow — Fast Rate of autumn production. 
H— h Broody — Non-Broody Instinct. 
N— n Smali — Large Egg-mode. 
C— ¢c Brown — White Egg-mode. 
