"238 The Microscope. 



Ooplasm very little as yet is known. In general it is stated by 

 various writers that the protoplasm is composed of the ultimate 

 elements of carbon, oxygen, hydrogen and nitrogen, and possi- 

 bly sulphur, the latter being sometimes found in it in small 

 •quantity. A ccording to all appearances the reticulum contains 

 a great quantity of plastin or some such substance, which makes 

 it more resistant to the dissolvents of ordinary albuminoides. 

 Lecithin is also probably present, as well as some of the globu- 

 lins, as vitellin and myosin, especially in young cells. At all 

 •events the quantity of plastin increases with the age of the cell. 

 The reticulum also appears to be saturated with water, holding 

 in solution some of the soluable substances of the surrounding 

 enchylema. 



The enchylema contains all the other substances composing 

 protoplasm, such as the nutritive matter introduced and as yet 

 not assimilated, etc. ; therefore, its chemical composition must 

 necessarily be very complex and very inconstant. 



III. Physiological function of protoplasm. — It is probably 

 true that the reticulum alone is endowed with the properties of 

 irritability and contractility ; it alone therefore, possesses the 

 power of effecting physical movements ; the enchylema, on the 

 contrary, remains always more or less passive in all such phe- 

 nomena. 



The enchylema, however, is the seat of all chemical movement, 

 such as the elaboration, the preparation, the digestion and 

 transformation of the nutritive principles; but as to the cause 

 and origin of the circulation of the more fluid portion of the 

 enchylema, I hesitate to pronounce myself; much study and ob- 

 servation are needed to give a satisfactory explanation of this 

 phenomenon, but that it is connected with the nutrition of the 

 cell appears to be the general opinion. 



IV. Inclavata and inclusions. — In young and even in many 

 adult cells, we find no other elements in the protoplasm than 

 the reticulum and the enchylema ; but this is not always the 

 case. On the contrary, there are often present in the protoplasm 

 bodies of various shapes and sizes and differing greatly as to 

 their nature, such for example as grains of starch and of aleur- 

 one, fat globules, granules and scales of vitellin, vacuoles, crys- 

 tals, etc. ; even foreign bodies are sometimes found in the proto- 

 plasm, such as Diatoms, Desmids, red blood corpuscles, grains 



