_/PR O TOP LA SM^ 



SUPER-MECHANICAL PROPERTI ES " 



This property of forming organs for temporary use, as required, is regarded 

 by von Uexkull (1909, pp. 11-32) as demonstrating the impossibility of ever 

 explaining protoplasmic activities on physico-chemical lines. This hopeless atti- 

 tude does not seem to me to be warranted. Many of these " organs " are formed 

 by the action of laws already known. Eor example, the Higftstivft vacuoles are 

 produced by the water takenin__with the food, and owe their shapp to an rf .<><* 

 tfvnsion ; if Higp.sf.ivft en7yjrngg_fl.rf> piwipnt in thn body of the protoplasm, they 

 wilL_naurall^_jind theiFway into the va/Minlft. , The pseudopodial changes of 

 form are in relation to changes of surface tension and consistency of the outer 

 layer of the protoplasm, as will be shown later. 



In this connection an interesting experiment is described by Rhumbler (1898, p. 249). If 

 a fine bit of glass rod be pushed against a drop of chloroform under water, it cannot be made 

 to enter the drop ; on releasing the pressure, it is^mmediately reyectectnf, on the contrary, 

 the rod be first coated with shellac, it is at once sucked hi. As soon as the shellac is dissolved 

 by the chloroform, the rod is thrown out again. I find it best to coat the glass with a filtered 

 solution of shellac in chloroform, and then to dry it, since ordinary shellac is only partially 

 soluble in chloroform. One might say that the chloroform will have nothing to do with 

 substances which it cannot digest, and when a mixed food particle is presented to it and 

 accepted, it digests a part and rejects the non-assimilable remainder. 



My object in quoting this experiment is to call attention to the way in 

 which quite simple combinations of well-known forces lead to the performance 

 of complicated and apparently purposeful results. With respect to the similar 

 process of the taking in of bacteria by leucocytes (phagocytosis), it is pointed 

 out by Ledingham (1912, p. 324) that leucocytes, when floating freely, are 

 spherical, and put out no pseudopodia unless in contact with some solid surface. 

 Vigorous shaking of the mixture of serum, leucocytes, and bacteria does not 

 affect the irigestion of the latter by the protoplasm, although there can be no 

 pseudopodial activity. When chance contact takes place, there is taking in of 

 the bacteria in a certain proportion of the encounters. The degree of phagocy- 

 tosis is, therefore, controlled by the number of encounters in unit time. There 

 is no indication of any kind of "seeking" on the part of the phagocytes. The 

 process seems to be one in which surface tension is the chief factor. It is also 

 obvious that, if the bacteria have been < aused to agglutinate into clumps, each 

 encounter will ensure' the ingestion of a arger number of organisms at a time ; 

 hence the " opsonic index " merely shows he presence of something that affects 

 the surface tension of the bacteria (see also the paper by Rhumbler, 1910). 



The " super-mechanical properties " of von Uexkiill are also supposed to intervene in the 

 activities of more differentiated structures, such as the muscle cells of actinia and so forth 

 (von Uexkull, 1909, pp. 72 and 73). Although I am unable to follow this investigator so far 

 as to deny all possibility of future explanation, there is no doubt that simple protoplasm 

 presents very difficult problems. It is, in fact, at present, impossible to understand how a 

 liquid, the properties of which protoplasm presents, as we shall see in a later page, can form 

 organs at all. At the same time, it must not be forgotten that the composition of a liquid 

 system is not of necessity the same throughout ; a drop of oil may be floating in dilute alcohol. 

 The various vacuoles in amoeba do not all contain the same substances in solution, as will be 

 seen in a later chapter. 



In connection with the subject of this section, it has also been pointed out that 

 animals and plants are units in time as well as in space ; they are compared to a 

 melody in music, whereas machines are merely units in space. It is supposed that 

 the human mind is unable to conceive such existences (see v. Uexkiill, 1909, 

 p. 28). But surely units in time are not wanting in the inorganic world. An 

 atom of radium has arisen from uranium, through an intermediate element, at a 

 certain time in past ages ; it changes again, at a definite rate, into helium and 

 niton, while the latter subsequently disintegrates into other elements. 



According to Rutherford (1913, p. 668), the life of uranium is about 1,000,000 years ; that 

 of ionium, 100,000 years; that of radium, 3,000 years; that of niton, 5 '55 days; that of 

 radium A, 4'32 minutes ; that of other intermediate products to radium F (polonium), 196 days; 

 and it is probably finally converted into lead. 



