ON THE MOLECULAR ORIGIH OF INFUSORIA. 
65 
' by the ashes of yeast.* That they may be induced by dead 
' organic matter, which has been subjected to a direct tempera- 
j ture of 150° or 200° centigrade — a heat utterly incompatible 
I with the existence of life — we have seen to have been proved 
by Pouchet, Jolly, Musset, and others. Whilst, then, the 
chemists have entirely failed in proving their case, the micro- 
scopical evidence is wholly opposed to the existence of atmo- 
, spheric germs. 
I The idea that these imaginary germs were the cause of putre- 
, faction, of disease, of blights among vegetables, and other evils, 
' originated with Kircher and the pathologists of the seventeenth 
I century. It has been frequently revived, but always shown to 
1 be erroneous. In 1852, cholera was supposed to be occasioned 
j by a fungus that really existed in the dejections, but which Mr. 
Busk pointed out was the uredo segetum of diseased wheat, 
which entered the body in the form of bread. Certain well- 
known parasitic diseases are spread by contact, such as scabies, 
which, as it depends upon an insect burrowing in the skin, 
may be understood to crawl from one person to another. Favus, 
or scald head, which consists of a parasitic plant growing on the 
scalp, also, I succeeded, in 1841, in proving might be commu- 
nicated to otherwise healthy persons ; f but many of our un- 
questionably infectious diseases, such as smallpox, scarlatina, 
measles, and typhus, have no such origin. It has been attempted 
to be proved, indeed, by Lemaire,| that in the condensed 
vapours of hospitals and other putrid localities, vibrios may be 
found ; but that vibrios are the cause of these various diseases, 
is not only not proved, but from what has been stated, is highly 
improbable. 
What, then, it may be asked, is the origin of the infusoria, 
vegetable and animal, that we find in organic fluids during 
fermentation and putrefaction ? In answer to this question, I 
answer they originate in oleo-albuminous molecules, which are 
formed in organic fluids, and which, floating to the 'surface, 
form the pellicle or proligerous matter. There, under the in- 
fluence of varied conditions, such as temperature, light, chemical 
exchanges, density, pressure, and composition of atmospheric 
air, and of the fluid, &c., the molecules, by their coalescence, 
produce the lower forms of vegetable and animal life. 
Hallier, describing the development of Penicillium crusta- 
ceum, tells us that, after all movement in the primary molecular 
mass has ceased, the molecules arrange themselves in long lines, 
which he calls Leptothrix chains (fig. 1, /). From the melting 
* Comptes-Bendus,” tome Ivi. pp. 418, 419. 
I t See the Author’s paper on Parasitic Fungi, — Trans. Royal Society of 
I Edinburgh, 1842.” 
X Comptes-Rendus,” tome lix. pp. 317-428 
VOL. VIII. XO. XXX. F 
