24 



VETERINARY PHYSIOLOGY 



they are often formed round material which has been taken 

 into the protoplasm, and that they are filled with a fluid 

 which can digest the nutritious part of the ingested particles. 

 In some cells, vacuoles may appear in the process of 

 disintegration. 



2. Activities. — (a). Many cells have the power of ingest- 

 ing foreisfn material. This phagocytic action plavs an 



V^C-'S-.-...i; :v..V" cJ-^^ ^ ■.- v-j-.4-;'r -■ - ■.■■"■>j;^-..-., .■..';'»-.■..;/ 

 Ai'-,' ,\^^ ( Nt ^Sx*.' ^^••■v '•■■'-r^tJ.-'J "")..'.: -■— •■;,/ Cj 



^^■m:i^y,^ 



Fig. 3.— Diagram of a Cell to show structure of Protoplasm and Nucleus. In 

 the protoplasm — A, attraction sphere enclosing two centrosomes ; T^, 

 vacuole ; C, included granules ; D, plastids, present in some cells. In 

 the nucleus — E, nucleolus ; F, chromatin network ; G, linin network ; 

 H, karyosome or nodal swelling. (WiLSOX.) 



enormously important part both in physiological and in 

 pathological processes in the body. 



(6) In certain cells, protoplasm undergoes changes in shape 

 {aTYwehoid movertient). This may be studied in the white 

 cells in the blood of the frog or newt. Processes ( jiseiido- 

 podia) are pushed out, and these are again withdrawn, or 

 the whole cell may gradually follow the process, and thus 

 change its position. 



