66 



"MALARIAL GERM/' 



A friend banded me on yesterday a report of the Section of Vegetable Pathology 

 for 18S6. In Plate II, Fig. 4, of tbis report, I find an illustration of what I suppose 

 is the cause of most of the diseases incident to this climate. The following extract 

 from the Texas Medical Journal contains an account of the discovery of what I 

 suppose to be the true "malarial germ." It was in Navarro County, Tex., dur- 

 ing the summer of 1861, that I noticed a deposit similar to dust upon the leaves 

 of the oak. Finding this upon leaves remote from ways of travel, where there 

 could be no suspicion of dust, I was prompted to make an examination ; but hav- 

 ing nothing to aid me except a small pocket microscope, I came to the conclusion 

 that it was simply mold. Bat if mold, why was it invariably found upon the upper 

 side of the leaf ? Why had it not formed during the previous wet spell, when the 

 earth was saturated with water*and vegetation filled with sap ? These and similar 

 reflections caused me to believe that this deposit was nothing but undeveloped spores 

 with which the atmosphere was filled during that season of the year; and that those 

 spores required, for their full development, heat and moisture, both of which would 

 be furnished by the sun and dew in which they were deposited. * * * If this hy- 

 pothesis be correct, then I thought that an atmosphere so vitiated would have a dele- 

 terious effect upon the human economy, and that each appearance of this deposit 

 would be followed by disease, the type of which would depend upon the quantity of 

 these spores in the atmosphere, as evidenced by the quantity of this deposit. Obser- 

 vation then fully convinced me of the truth of that hypothesis. And now, after an 

 observation and experience of more than a quarter of a century in Texas, I am fully 

 persuaded that the cause of malaria is a spore, which rises from a dry, though pre. 

 viously wet soil, and is suspended in the atmosphere until washed out by a general 

 rain-fall. That the sample sentyou by Dr. Osburn was deposited with the dew, upon 

 the leaf, and developed into a visible germ by the action of the sun, there can I think 

 be no possible doubt. — (John L. Felder, Cleybourne, Tex.) 



Answer. In reply to your inquiries concerning tlie so-called " malarial 

 germ," I would say that the substance that you describe as occurring 

 upon oak leaves is probably one of the common powdery mildews which 

 is abundant throughout the entire country. This mildew is a true plant, 

 just as much so in fact as the oak upon which it occurs ; it of course 

 differs greatly in habit from the latter and it is placed much lower in 

 the plan of nature. There is fully as much difference, however, between 

 the germs which are believed to be the cause of many diseases of the 

 human family and the mildew upon the oak as exists between the former 

 and the oak itself. 



To botanists the mildew occurring upon oak leaves is known as 

 Microsphceria quercina, and like all true plants it lives, grows, produces 

 bodies analogous to seed, and filially dies. The black capsules men- 

 tioned as being found upon the leaves are the sacs or receptacles which 

 contain the spores or reproductive bodies of the fungus. The spores 

 are produced late in the summer and they fall to the ground with the 

 leaves, remain dormant during the winter, and the following spring 

 are set free, and, being very light, are easily wafted from place to place 

 by the wind. When they fall upon the oak leaves and the proper con- 

 ditions of moisture and heat are present they germinate and give rise 

 to the same kind of whitish threads from which they were derived. As 



