274 ANNUAL OF SCIENTIFIC DISCOVERY. 



cules of organic matter are exposed to the action of the air. This is probably 

 the cause of the efficacy of deep harrowing or plowing. Manures produce a 

 large quantity of carbonic acid, and most when most decomposed. For ex- 

 ample : 1st. Fresh cow-dung gives off, in 24 hours, 12 litres of carbonic acid 

 per square metre ; if kept for 4 days it gives about 20 litres of gas from the 

 same superficies. 2d. Fresh 'horse-dung^ only exhales 5 litres of carbonic 

 acid per square metre in 24 hours. After 4 days the fermentation becomes so 

 considerable that the production of gas rises to 88 litres per square metre in 

 24 hours. The thickness of the layers experimented on was uniformly 8 cen- 

 timetres. Dry sugar and moist wood alcohol do not produce carbonic acid ; 

 guano exhales a very small quantity ; 1 kilogram of unbleached flax disen- 

 gages spontaneously from 11 to 12 litres in 24 hours, after having been ex- 

 posed to the air in a damp state for 3 or 4 days. The temperature during 

 these experiments varied from 68 to 86 Fahrenheit. The results of these 

 experiments show that the quantity of carbonic acid furnished to vegetables 

 by the decomposition of the organic matters in the soil, is more consider- 

 able than has hitherto been supposed. It is pretty generally admitted that 

 the carbonic acid necessary to vegetation is due almost entirely to the respira- 

 tion of animals, and ponderation has been established between the two 

 kingdoms which has been, perhaps, too absolute, when we consider the great 

 quantity of carbon annually fixed in the mass of vegetables which cover the 

 cultivated portions of the earth, and the comparatively small relative quantities 

 of carbonic acid furnished by the respiration of animals. My experiments 

 appear to me destined to prove that if we consider the amount of carbonic 

 acid emanating from animal respiration, combustion, and volcanoes, it will 

 still be necessary to attribute to the production of carbonic acid from the 

 surface of the earth the greater share in the alimentation of vegetables. It is 

 rational to admit from the above that vegetables are placed on the surface of 

 the earth in an atmosphere charged with carbonic acid, which is perpetually 

 being renewed, and is the most abundant when the temperature is high and 

 the soil moist circumstances which aid the decomposition of manures. 



ON THE ORIGIN OF GOITEE. 



M. Maumene, of France, has recently been engaged in investigating the 

 causes of goitre, or the frightful swelling of the glands of the neck so common 

 in Switzerland and some districts of France. Goitre is undoubtedly due to 

 the action of certain waters in particular cases. Some young men have been 

 known to give themselves goitre in 2 or 3 months to escape military service ; 

 successive families have been found to be attacked with goitre when they oc- 

 cupied houses on certain streams ; even animals develop it in these condi- 

 tions. M. Maumene, suspecting that the fluorid of calcium might have an 

 important influence, administered this salt, together with the fluoride of so- 

 dium, to a small dog for about 4 months. The effect was to produce an 

 enlargement of the neck to such an extent as to attract notice, which enlarge- 

 ment has remained permanent. 



