84 STATE BOARD OF AGRICULTURE. 



Mosquitos (Anopheles, disease-carrying. Culex, harmless). Diseases 



transmitted — yellow fever, malaria and filariasis. Chart to show how 



mosquitos carry disease. Chart showing how to distinguish ordinary 



from disease-carrying mosquitos. 

 Fleas (Pulex cheopis). — Rat fleas carry bubonic and septicemic plague. 



Common flea or dog flea (Ctenocephalus serraticeps) is said to be a 



carrier of infantile paralysis. 

 Tsetse fly. — (Olossina palpalis). Carrier of Trypanosome gambiense, which 



produces sleeping sickness. 

 Texas fever ticks (BoopMlus hovis). — Carrier of Piroplasma Mgeminum 



the protozoa of Texas cattle fever. 



TV. Chejmical Disinfectants. 



Coal tar products (phenol, cresol, petroleum, creosote). Products of distilla- 

 tion of wood (creosote, rmethyl alcohol). Anllin dyes. Mineral acids and 

 salts, (mercuric bichloride, borax, copper sulphate, ferrous sulphate, calcium 

 hypochlorite or bleaching powder). Organic acids (acetic, lactic, salicylic 

 acids). Organic salts (benzoate of soda), chlorine, iodine, sulphur, dioxide. 

 Formaldehyde. Alcohol. Hydrogen peroxide. 



V. Physical Disinfectants. 

 Cold — Ice box or refrigerator. 

 Heat — Sterilization or pasteurization by boiling (water, foods), by steam 



(clothing), or by hot air (bedding), cremating. 

 Sunlight — Culture of B. prodigiosus killed by light. 



E. MICROBIOLOGY OF SOILS. 



I. Demonstration of Microorganisms in soil. 



A sample of soil direct from the field from which plates have been poured, 

 hanging drops and stained slides prepared. Comparative numbers in differ- 

 ent soil types. With the same dilutions, plates have been poured from sands, 

 clays, loams, mucks, etc., from the same and from different localities. Com- 

 parative numbers in the different soil strata. Plates demonstrating the con- 

 stantly decreasing number of organisms in surface, subsurface, and subsoil. 



IT. Functions of Microorganisms in Soil. 



1. Action Upon Minerai, Matter. 



As a rock decomposes microorganisms take hold and grow and by their 

 life and death followed by that of higher plants fertile soil is produced. 

 The insoluble compounds of phosphorus, sulphur, iron, etc., are made 

 soluble by the activity of microorganisms. Demonstrated by increased 

 amount of soluble phosphate when inoculated. 



2. Action Upon Organic Matter. 



Decomposition of organic matter in soil as elsewhere is largely due to 

 microorganisms. Demonstrated by there being no decomposition when 

 bacteria are killed. This is true of all forms of organic decay. Humus 

 production, cellulose decomposition, commercial organic fertilizers' avail- 

 ability are demonstrated. In this decomposition, there is a great deal 

 lost in the gaseous form but recovered by other bacteria. Shown in the 

 "Nitrogen Cycle." Decomposition in the manure heap with attendant 

 losses. Straw decay in manure shown to be caused by bacteria. 



TTI. Factors Influencing Soil Microorganisms. 



1. Cultivation. 



J Plates poured to show varying numbers on fields managed in different 



manners. 



2. LrMiNG 



Or acidity and alkalinity. Shown by plating as above and also data. 



3. Influence of Methods of Managing Manures. 

 Upon the microbial activity and elemental losses. 



