§ V.J Origin and distribution. 43 



stances. To give some idea of the approximate numbers it may 

 be added, that the number of germs in the air caught on glass 

 plates in a mixture of glycerine and grape-sugar in the aspirator, 

 Fungi and Bacteria capable of development and in some cases 

 dead being taken together, varied in the garden of Montsouris, 

 in a single series of observations, from between 0-7 to 3-9 in 

 December and to 43-3 in July in a litre of air. 



The most exact air-determinations have been recently carried 

 out by Hesse with the aspirator and gelatine-process. These 

 showed the presence of germs capable of development in a litre 

 of air, as follows : 



In Sick-ward No. i, with 17 beds. Bacteria 2-40, — Moulds 0-4. 

 » » 2, „ 18 „ „ ii-o, „ i-o. 



Cattle-stall for experimental pur- 

 poses belonging to the Na- 

 tional Oifice of Health : (a) „ 58-0, „ 3-0. 

 (b) „ 232.0, „ 28-0. 



The air out of doors in Berlin was found to contain o- 1-0-5 

 germs per litre, of which about half were Fungi and half 

 Bacteria. 



Miquel obtained thirty-five germs per cubic centimetre in 

 rain-water caught as it fell, sixty-two in river-water from the 

 Vanne ; in that from the Seine above Paris 1 400, below 

 Paris 3200. 



We have no numerical determinations of the number of germs 

 present in the soil; but we can produce growths of Fungi and 

 Bacteria from every small pinch of soil taken from the surface 

 of the ground. In lower strata, according to some preliminary 

 researches made by Koch (14) in winter, the number of germs 

 capable of development diminishes rapidly. 



A special interest attaches to the question of the presence of 

 germs in and on sound living organisms. That they must remain 

 hanging in profusion to the surface of such organisms is obvious 

 from the preceding statements, and is proved by every investiga- 

 tion. They can penetrate into the interior of the higher forms of 



