PRODUCED BT THE MOSQUITOS. 285 



lijjlit, heat, and moisture which, while it favours the action 

 ot chemical affinities, accelerates the putrefaction of organ- 

 ised substances. May not the mosquitos themselves in- 

 eivase the insalubrity of the atmosphere ? When we reflect 

 that to the height of three or four toises a cubic foot of air 

 is often peopled by a million of winged insects,* which 

 contain a caustic and venomous liquid ; when we recollect 

 that several species of culex are 1*8 line long from the head 

 to the extremity of the corslet (without reckoning the legs); 

 lastly, when we consider that in this swarm of mosquitos 

 and gnats, diffused in the atmosphere like smoke, there is 

 a great number of dead insects raised by the force of the 

 ascending air, or by that of the lateral currents which are 

 caused by the unequal heating of the soil, we are led to 

 inquire whether the presence of so many animal substances 

 in the air must not occasion particular miasmata. I think 

 that these substances act on the atmosphere differently from 

 jand and dust; but it will be prudent to affirm nothing 

 positively on this subject. Chemistry has not yet unveiled 

 the numerous mysteries of the insalubrity of the air ; it has 

 only taught us that we are ignorant of many things with 

 which a few years ago we believed we were acquainted. 



Daily experience appears in a certain degree to prove the 

 fact that at the Orinoco, Cassiquiare, Rio Caura, and where- 

 ever the air is very unhealthy, the sting of the mosquito 

 augments the disposition of the organs to receive the im- 

 pression of miasmata. When you are exposed day and 

 night, during whole months, to the torment of insects, the 

 continual irritation of the skin causes febrile commotions ; 

 and, from the sympathy existing between the dermoid and 

 the gastric systems, injures the functions of the stomach. 

 Digestion first becomes difficult, the cutaneous inflamma- 

 tion excites profuse perspirations, an unquenchable thirst 

 succeds, and, in persons of a feeble constitution, increasing 

 impatience is succeeded by depression of mind, during 

 which all the pathogenic causes act with increased violence. 

 It is neither the dangers of navigating in small boats, the 

 eavage Indians, nor the serpents, crocodiles, or jaguars, that 

 make Spaniards dread a voyage on the Orinoco; it is, as 



It ii sufficient to nrention, that tbecuoic foot contains 2, 985, 981 cubic 

 ttt, 



