

1920] 



MACDOUGA l—biocolloids 



133 



7 



the swellings is a means of recording phenomena not to be evaluated 

 in any other manner 5 (fig. 2). 





Fig. 2. — Auxograph arranged to record changes in thickness of trio of sections 

 of colloidal material; tip of pointed glass tube, sealed to vertical swinging arm ( 

 (smaller figure), rests in socket in center of thin triangular glass plate B f which lies 

 on sections A; expansion of sections pushes this arm upward (adjustment at / ; placed 

 to give an amplification of 20 in cut), compound lever being arranged to give a down- 

 ward movement of pen; record slip, daily or weekly, 8 cm. wide, is ruled to mm. 

 (not shown in cut). Illustration made to show action of trio of sections of agar in 

 water at end of 1 . 5 hours. 



s For description of this apparatus see MacDougal, D. T.. Hydration and growth. 

 Publ. no. 297. Carnegie Inst. Wash. 1919. 





