Amount manufactured: 14,600 gallons (292 barrels)
| 12,600 gallons crude carbolic acid at 12 cents per gal. | $1,512.00 |
| 12,300 pounds rosin at $2.48 per hundred | 305.04 |
| 2,550 pounds caustic soda at $3.70 per hundred | 94.35 |
| 2 tons coal at $5.00 per ton | 10.00 |
| Labor | 94.46 |
| Supervision. | 50.00 |
| Total | $2,065.85 |
| Cost per gallon | 14.14 |
To insure the manufacture of a uniform product, requisitions called for crude carbolic acid of a specific gravity not greater than 0.97, and to contain not less than 15 per cent tar acids. Each consignment of crude carbolic acid received was assayed at the laboratory to determine its specific gravity and percentage of tar acids, for it is necessary to keep the product of a specific gravity approximately that of water, so that it will diffuse rapidly and neither sink to the bottom, nor remain at the surface.
In a hundred square miles of territory treated we used about two hundred barrels of this mixture a month. The cost of manufacture was about seventeen cents a gallon. In the early days we had used various proprietary articles for this purpose, for which we generally had to pay about fifty cents per gallon. Larvacide came in the course of time to be used on the Isthmus for disinfectant purposes of many kinds, and also for the prevention of fly-breeding. We found it most excellent for all rough purposes of this kind, such as disinfecting and deodorizing around privy vaults and similar places.
A sanitary inspector, when malaria is rife, has to be thoroughly familiar with the life history of the mosquito, and particularly with the life history of the anopheles. There are some six or seven hundred species of mosquitoes, and many of these differ widely in their habits of flight. The stegomyia mosquito is one of the feeblest species in its ability for flight, and it is at once blown away and destroyed when it gets into a breeze. It therefore seldom wanders from the house in which it is bred. The culex solicitans is very strong and bold in flight, and can fly twenty miles in one night before a favoring breeze. This has been demonstrated by Dr. J. B. Smith, of New Jersey. Dr. Smith was the entomologist of the state of New Jersey, and one of the most faithful and successful mosquito workers.
The culex solicitans is the common gray mosquito which breeds so abundantly in the salt-water marshes of our Atlantic coast. The different species of mosquitoes differ widely as to their breeding-places, some species breeding in brackish water, some only in fresh water. Other species breed freely in dirty and muddy water, and still others can apparently live only in fresh, clean water. The two species with which we are most concerned as being disease-carrying mosquitoes are very particular as to their habits, always seeking fresh, clean, clear water in which their larvæ can develop.
The stegomyia likes clean rain water such as is found in cisterns and water barrels. As these collections are found principally around the dwellings of man in towns and cities, this mosquito is known as a town mosquito. The larvæ of the anopheles, the malarial mosquito, also likes clear, clean, fresh water, but it requires algæ and grass for its protection. These conditions are best furnished by the edges of ponds and running streams. This mosquito is, therefore, essentially a country mosquito.
Generally, in any one locality, there are only three or four species of mosquito occurring in any abundance, so that when the inspector has learned to differentiate these, he is pretty well educated for work in that particular locality. Each species usually has some prominent trait; the anopheles, for instance, has the hind legs very much longer than the fore legs, which gives her when at rest the appearance of standing on her head. The stegomyia has prominent white markings on its body and white bands around the joints of its legs, and while these cannot readily be distinguished by the naked eye, they give it a gray appearance which easily distinguishes it from other species in such a locality as Panama.
The culex solicitans and stegomyia look very much alike to the naked eye, so much so that one of our most experienced inspectors at Panama, on returning from a vacation spent on Long Island, told me that the stegomyia was the common mosquito on Long Island. As a matter of fact, the stegomyia never appears farther north than Norfolk, Virginia, unless as a matter of accidental introduction during warm summer weather.
As the inspector deals with the mosquito in the larval stage principally, he must be familiar with the habits of the larvæ, and the habits of the different larvæ differ about as much as the habits of the adult mosquitoes. They also differ much in size and shape; for instance, the larvæ of the anopheles can readily be recognized by the way it comes to the surface to breathe. During this process it lies horizontal to and in contact with the surface of the water. The culex larvæ, when breathing, lies with its tail up and head down. The anopheles is a long, very slender larva; the culex, short and chunky. The anopheles larva is most noticeable from its superior intelligence. It will dive and seek shelter in the grass at any sound or shadow thrown upon the water; the culex larva is sluggish and pays little attention to such things.