M. MATERIA MEDICA, THERAPEUTICS, AND HYGIENE. 543 

 PHYSIOLOGY OF MUSQUITO CURTAINS. 



A suggestion that musquito curtains in tropical countries, 

 besides keeping off these pests, also serve as screens against 

 miasma, has elicited various corroborating statements from 

 travelers and others ; and we find in a recent number of Na- 

 ture an indorsement by Mr. E. L. Layard, the eminent natu- 

 ralist of South Africa, as to a beneficial action in this direc- 

 tion. He finds that even so slight an obstruction as the fibre 

 of the net causes a great difference in the temperature be- 

 tween the interior and exterior air, this difference amounting 

 in some instances to eight degrees, the increased temperature 

 of the inside tending to dissipate the malaria, and prevent 

 the cold and damp of the tropical night from acting upon the 

 system when relaxed in sleep, and with the pores of the skin 

 wide open. 12 A, June 23, 143. 



BALESTEA OX THE MIASM OF THE PONTINE MAESHES. 



Mr. Balestra, in a series of investigations upon the nature 

 and origin of the miasma of the Pontine Marshes, found the 

 stagnant waters filled with organisms of various sj)ecies, and 

 among them one in particular, which was abundant in pro- 

 portion to the degree of putrefaction in the water. This is 

 a small alga, which floats on the surface of the water, and 

 presents the appearance of drops of oil. At a low tempera- 

 ture these germinate very slowly ; but during the warm 

 weather, and when exposed to the air, they reproduce very 

 rapidly. The author, finding that the addition of a small 

 quantity of arsenious acid, or sulphite of soda, or, still better, 

 of the neutral sulphate of quinine, destroyed the vitality of 

 this plant, infers that the miasma of the marshes is due to its 

 existence and propagation, and that the well-known agency 

 of these medicaments in curing fever depends upon their 

 chemical action upon the plant which causes it, especially as 

 its spores are found to be disseminated every where through 

 the atmosphere.. The plant is not developed in a dry season, 

 although it makes its appearance in great quantity during 

 moderately rainy weather occurring in a warm season. The 

 non-occurrence of the fever in the winter, according to the 

 author, is due less to the cold, which prevents the vegetation 

 of the plant or retards the decomposition of organic sub- 



