562 SECTIONAL TRANSACTIONS.— D. 



Afternoon. 



Joint Meeting witli Sections I and K for communications on Experi- 

 mental Biology : — 



Prof. J. H. Priestley. — Factors affecting Cell Growth. 



In the flowering plant, growth, as represented by increase in cell size and subsequent 

 cell division, takes place in very different ways in different regions of the plant. Two 

 main types of cell multiplication can be distinguished, one characteristic of the apical 

 meristem, the other characteristic of the region of shoot or root just behind the apical 

 meristem. These two types of cell growth are defined and the internal factors contri- 

 buting to their maintenance discussed. In the intercalary meristems, vascular 

 cambium and cork phellogen, both types of cell growth, can also be recognised. Thus 

 in corkE ormation different types of cell growth are characteristic of Monocotyledon 

 and Dicotyledon, and in the vascular cambium ray initials and fusiform initials show 

 different characteristics. 



The organisation of growth in the shoot is considerably elucidated by a clear 

 recognition of these different types of cell growth. Vascular differentiation, in relation 

 to cell growth, supplies the key to the ' articulate ' development which is its character- 

 istic feature. 



Dr. W. H. Pearsall. — The Absorption of Methylene Blue and Orange G. 

 by Plant Tissue in relation to the H. ion Concentration. 

 Absorption of an acid and a basic dye by potato tissue varies with the H ion 

 concentration. In the region of ^H 6-5 the basic dye (methylene blue) is strongly 

 absorbed and the acid dye (Orange G) is very weakly absorbed. About pK 3-0 the 

 basic dye absorption is greatly reduced and acid dye absorption greatly increased. 

 The increase in acid dye absorption is constantly about 1-5 times greater than the 

 reduction in basic dye absorption. Since these variations irn dye absorption are 

 shown both by living and by dead (etherised) tissue, it is assumed that they are due 

 to combination of the dyes with substances having ampholytic properties. Analysis 

 shows that these substances would be iso-electric about pB. 4-2— 4-5, a figure reasonably 

 near to the iso-electric point (pB. 4-3-4-4) of the principal potato protein. 



Dr. 0. W. TiEGS. — The Double Helicoid Structure of Muscle. 



The occurrence of striations (discs) in muscle fibres is inferred from the fact that 

 in thin microtome or optical sections they present the appearance of successive 

 transverse lines. Now unless the section be taken along its axis a helicoid or double 

 hehcoid will present a similar appearance. It is found in reality that if the focus bo 

 taken precisely along the axis of a muscle fibre a double helicoid arrangement of the 

 striae can be detected. 



Prof. A. J. Clark. — The Oxygen Consumption of the Frog's Heart. 



The conclusions reported are based on a series of experiments carried out by 

 Dr. A. C. White and the author. 



Three methods were used. In methods 1 and 2 we measured the oxygen removed 

 from air in contact with hearts perfused with Ringer's solution ; in the first method 

 the whole heart was used, and in the second the ventricle alone. In the third method 

 we measured the oxygen removed from a suspension of red blood corpuscles in Ringer's 

 fluid placed in the ventricle. The three methods gave concordant results. 



We found, in agreement with Starling and Visscher's work on the dog's heart- 

 lung preparation, that the oxygen consumption depended on the diastolic volume 

 of the ventricle, and that it was not increased by increasing the resistance against 

 which the ventricle contracted. Prolonged perfusion with Ringer's fluid reduced the 

 oxygen consumption to about one half the original value, and also reduced the 

 mechanical response, but the addition of serum or of soaps restored both factors to 

 their original value. 



The resting oxygen consumption of the heart was from 20 to 30 per cent, of that 

 occurring during moderate activity. Removal of calcium, excess of potassium. 



