THE BEGINNINGS OF LIFE. 279 



size and specific gravity ought also to be able to pene- 

 trate, and to be as easily recognizable. 



The wide distribution of starch throughout the atmo- 

 sphere and in the respiratory organs of animals was 

 first pointed out by M. Pouchet. It presents itself 

 under two principal modifications : (i ) in its natural con- 

 dition, and (2) as it exists after having undergone a pro- 

 cess of cooking. In the majority of cases it exists in the 

 former state ; but it is also often met with, in the most 

 varied situations, either simply swollen or quite burst 

 by the action of heat ^ Such swollen or burst granules 

 which are swept about in the atmosphere are probably 

 derived from microscopical fragments of bread. In 

 addition to its swollen or cracked appearance, this form 

 of starch is characterized by the fact that it is not 

 so strongly coloured by iodine as that which is in its 

 normal condition. The particles of starch are met with 

 of almost all sizes below -^\^' of an inch in diameter — 

 which is about the magnitude of the largest granules. 

 The larger ciliated Infusoria, however, vary from 

 -^' to 24if" i^ diameter ; whilst their eggs, according 

 to Balbiani^ are not less than from -Yi-^-^' to ^ }^ j'" in 

 diameter, so that they would be as easily appreciable 

 wherever they existed as the starch granules themselves, 

 which seem to be so much more ubiquitous. The 



^ M. Pouchet also occasionally found starch granules of a bright blue 

 colour. The cause and nature of this colour-modification is very 

 obscure (see ' Compt. Rend.' i860, 1. 1. p. 572), though it may be due to 

 the presence of minute quantities of iodine in the atmosphere. 



