RECENT ADVANCES IN SCIENCE 565 



iodine together with dextrin, (2) formaldehyde and dextrin 

 both liquefy starch, (3) a mixture of starch and formaldehyde 

 has a greater reducing power towards Fehling or Pavy solu- 

 tions than the same quantity of formaldehyde alone ; (4) if a 

 mixture of starch and formaldehyde is dialysed the dialysate 

 contains in addition to formaldehyde a fermentable sugar, 

 possibly a mixture of maltose with isomaltose. Woker and 

 Maggi (Berichte, 191 7, 50, n 89) also point out that formal- 

 dehyde can apparently act as a hydrogenase since a solution 

 of lead acetate containing formaldehyde and sulphur darkens 

 rapidly at ioo° or more slowly if exposed to light at the 

 ordinary temperature ; this phenomenon is attributed to a 

 hydrogenation of the sulphur by the formaldehyde. The 

 fact that lead acetate is more soluble in formalin than in water 

 is explained by assuming that formaldehyde combines in some 

 way with lead, after which polymerisation to formose results, 

 and a similar reaction with the magnesium in chlorophyll is 

 supposed to precede the polymerisation of formaldehyde to 

 formose in green plants. 



The action of formaldehyde on lactose, maltose, and sucrose 

 has been re-investigated by Heiduschka and Zirkel (Arch. 

 Pharm. 191 7, 254, 456) ; the products obtained when this 

 substance acts upon bioses in aqueous solution may contain up 

 to 39 per cent, of formaldehyde ; they are not definite chemical 

 compounds but are most probably solid solutions of formal- 

 dehyde in the sugars. 



The existence of accessory factors in plant growth similar 

 to vitamines in animal growth is discussed by Rosenheim 

 (Biochem. J. 191 7, 11, 7), who has shown that aqueous extracts 

 of Bottomley's bacterised peat have very marked growth- 

 stimulating properties ; such extracts give precipitates with 

 phosphotungstic acid which similar extracts from ordinary 

 peat do not give. 



The presence of silica in most tissues has been demon- 

 strated by Gonnermann (Zeitschr. physiol. Chem. 191 7, 99, 

 255). Expressed as percentage of total ash the quantities are 

 as follows : Hair, 3-20 ; milk, 0*3 to 0*4 ; thymus, 8 ; 

 adrenals, 7-16; blood corpuscles, 3; serum, 2-3; muscle, 

 2-4; intestine, 2-13. Good effects appear to have been 

 observed after the administration of silicic acid in cases of 

 tuberculosis, and while most herbs contain considerable quan- 



