On the Physiology of the Silkworm

THE digestive enzymes of Lepidoptera and other invertebrates appear to warrant a closer study than has as yet been accorded to them, more especially on account of the prevailing alkalinity of the secretions. Those of the silkworm were investigated by Sawamura [1900][1901][1902], a summary of whose work, together with that of earlier investigators, is given below. It seemed of interest however to examine some of the actions more fully with the aid of indicators, whereby the hydrogen ion concentration could be measured with very approxi- mate accuracy according to the method as improved by Clark and Lubs [1917]. In this connection the recent publication with coloured plates by Clark [1920] proved specially useful.