The Organism as a Whole, from a Physicochemical Viewpoint

by Jacques Loeb

Influence of Temperature upon the Time (in Minutes) Required From Insemination to the First Cell Division

Temperature		Arbacia				Strongylo­centrotus purpuratus
		Loeb and Wasteneys 1911		Loeb and Chamberlain 1915
°C.		Minutes		Minutes		Minutes
3						532
4						469
5						352
6						275
7		498				291
8		410		411		210
9		308		297	.5	159
10		217		208		143
11		175		175
12		147		148		131
13				129
14				116		121
15		100		100		100
16		85	.5
17		70	.5
18		68		68		187
19				65		178
20		56		56		175
21				53	.3	178
22		47		46		175
23				45	.5	Upper temperature limit
24				42
25		40		39	.5
26		33	.5
27	.5	34
30		33
31		37

These figures permitted the determina­tion of the temperature coefficients Q₁₀ with a sufficient degree of accuracy (see next table). It seemed of importance to attempt to decide what the chemical reac­tion underlying these reac­tion velocities is (if it is a chemical reac­tion). Loeb and Wasteneys[255] investigated the temperature coefficient for the rate of oxida­tions in the newly fertilized egg of Arbacia and found that the temperature coefficient Q₁₀ for that process does not vary in the same way as the temperature coefficient for cell division.

TABLE XI

Temperature Coefficients Q₁₀ for the Rate of Segmentation and Oxidations in the Eggs of Strongylocentrotus AND Arbacia

Temperature		Q10 for Rate of Segmentation in		Q10 for Rate of Oxidations in Arbacia
		Strongylocentrotus	Arbacia
°C.
3–	13	3.91		2.18
4–	14	3.88
5–	15	3.52		2.16
7–	17	3.27	7.3	2.00
8–	18		6.0
9–	19	2.04	4.7
10–	20	1.90	3.8	2.17
11–	21		3.3
12–	22	1.74	3.1
13–	23		2.8	2.45
15–	25		2.5	2.24
16–	26		2.6
17.5–	27.5		2.2	2.00
20–	30		1.7	1.96

It is obvious that the temperature coefficient of the rate of oxida­tions is remarkably constant, about 2 for 10°, for various temperatures and does not show the varia­tion from 7 or more to 2.2 for Q₁₀ for the rate of segmenta­tion.

Kanitz[256] has shown that in a graph in which the logarithms of the segmenta­tion velocities are drawn as ordinates and the temperatures as abscissæ the logarithms form two straight lines which are joined at an angle. According to the law of van’t Hoff and Arrhenius concerning the influence of temperature upon velocities of chemical reac­tions the logarithms should lie in a straight line. We are dealing therefore in these cases with two exponential curves, one representing in Arbacia the interval 7–13° and the second from 13–26°; in Strongylo­centrotus between 3–9° and 9–20°.

It was found in these experi­ments that if measurements of the Q₁₀ of later stages of development are attempted the varia­tions due to unavoidable difficulties become too great to permit an equal degree of reliability in the determina­tions.

The vast importance of this influence of temperature upon the rate of development is seen in the fact that in addi­tion to the food supply the rate of the maturing of plants and animals depends on this factor.