(44) 



me to look for means of expressing snch changes in hardness more 

 accurately in measure and number, as an approximate determination 

 would not do here. 



A communication by J. von Uexküll x ) on the 18 th of April last 

 "Die Verdichtung der Muskeln", led me to a separate description of 

 my investigations about the determination of hardness in muscles. 

 In this communication he says: "wir besitzen zwar kein geeignetes 

 Instrument, um das Hartwerden der Muskeln zu messen", while he 

 winds up as follows : "Ich habe geglaubt, auf diese wichtige, aber 

 allzusehr vernachliissigte Eigenschaft der Muskeln hinzuweisen, in 

 der Hoffnung, dass sich jemand findet der einen brauchbaren Apparat 

 konstruiert, um die Muskelverdichtung unabhangig von der Muskel- 

 verdickung zu registrieren." 



For many decades together mineralogists have made determination 

 of the hardness of materials, in which a number of methods were 

 employed, which, however, in that form could not be applied 

 to living objects. The literature only gathers for what is called 

 hardness in general, data, for which I refer to some authors 2 ) in 

 behalf of those who wish to become more thoroughly acquainted 

 with the subject. 



Hardness is a collective idea, including and typifying an amount 

 of qualities: cohesion, elasticity, plasticity, gliding, splitting and 

 fracture. It is on the value which in a concrete case is assigned 

 more especially to one of the qualities mentioned, that depends the 

 general detinition which shall be given of hardness. For living 

 objects gliding, splitting and fracture need not be taken into account. 

 I desist from a more detailed separate description of the three 

 remaining qualities: cohesion, elasticity and plasticity. But if these 

 three qualities are paid attention to, Auerbach's 3 ) definition of hardness 

 will no doubt be agreed to : "Harte ist eine Art von Festigkeit, 

 namlich der Widerstand gegen die Bildung von Unstetigkeiten oder 

 dauernden Deforrnationen beim Drucke zweier spharischer Oberllachen 

 gegen einander, und kann Eindringungsfestigkeit genannt werden . . . 

 Sie ist quantitativ durch den Grenzeinheitsdruck im Mittelpunkte 

 der Druckflache bestimmt." 



!) J. v. Uexküll. Die Verdichtung der Muskeln. Originalmitteilung. Zentralblatt 

 für Physiologie. Bd. XXII N°. 2. 



2 ) H. Rosenbusch und E. A. Wülfing. Physiographie Allgemeiner Teil. Stuttgart 

 1904. 



G. Tschermak. Lehrbuch der Mineralogie. Wien 1905. 



Egon Muller. Ueber Hartebestimmung Inaug. Dissert. Jena 1906. 



3 ) F. Auerbach. Kanon der Pbysik pag. 119. Leipzig 1899. 



