176 



VITAL PHENOMENA OF PROTOPLASM. 



minute veins and find their way into the surrounding connective tissue, where they 

 may further continue to exhibit amoeboid movements. Corpuscles which have 

 thus emigrated from the vessels are known as " wandering cells," and the process of 

 emigration is known as " diapedesis." Although probably occurring to a certain 

 extent normally, it is greatly increased in inflammatory conditions of the tissues. 



Inception of foreign particles. When any foreign particle comes in contact 

 with a free cell, the particle adheres to it, becomes enwrapped by processes of the 

 protoplasm, and is then drawn gradually into the interior, where it may remain 

 for some time without change, being moved about by any currents which exist 

 in the cell, and carried along by the changes of place which the cell undergoes 

 (see fig. 204). Eventually such foreign particles may be extruded again. If, on the 

 other hand, the particle is of considerable size as compared with the protoplasm 

 with which it comes in contact, the latter extends around and over it so as to 

 envelop it more or less completely. This phenomenon of inception seems thus to 

 be dependent upon amoeboid movements of the protoplasm. 



Conditions influencing the contractile manifestations of protoplasm. 

 All the several manifestations of contractility are influenced in the same manner by 



i. 



r. 



Fig. 204. CHANGES OF FORM OF A WHITE CORPUSCLE OF NEWT'S BLOOD, SKETCHED AT INTERVALS OF 



A FEW MINUTES. THE FIGURES SHOW ALSO THE INTUSSUSCEPTION OF TWO SMALL GRANULES, AND 

 THE CHANGES OF POSITION WHICH THESE UNDERWENT WITHIN THE CORPUSCLE. (E.A.S.) 



similar external conditions. Thus it is found that variations of temperature have 

 a marked effect upon all. In warm-blooded animals the phenomena cease altogether 

 to be exhibited, if the protoplasm which is under observation is cooled to below a 

 temperature of about 10 C., although they will be resumed on warming the 

 preparation again, and this even if it has been cooled to C., or a little lower. 

 And when warmed gradually, it is found that the movements become more active 

 as the temperature rises, attaining a maximum of activity a few degrees above the 

 natural temperature of the body, although if maintained at an abnormally high 

 temperature, they are not long continued. A temperature a little above this 

 maximum, rapidly kills protoplasm, producing a stiffness or coagulation in it 

 (heat-rigor) which is preceded by a general contraction. From the condition of 

 rigor the protoplasm cannot be recovered. 



The contractility of protoplasm is dependent upon supply of oxygen. If this be 

 withheld, the movements will, it is true, proceed for a time as usual, but this is 

 because protoplasm, like other forms of contractile substance, such as muscle, has 

 the power of storing away and using oxygen in some form of combination. For it 

 is found that the active manifestations will not proceed indefinitely in the absence 

 of oxygen, but cease after a time, to be renewed only on the accession of fresh 

 oxygen. 



