50 THE LIFE OF PASTEUR 



and nothing was easier than to recognize their hemihedral 

 character. " I accept with great pleasure," wrote Biot on 

 April 7, "the offer you make me of sending me a small 

 quantity of your two acids, with models of their crystalline 

 types." He meant the righthand tartaric acid and the left- 

 hand tartaric acid, which Pasteur — not to pronounce too hastily 

 on their identity with ordinary tartaric acid — then called 

 dextroracemic and Icevoracemic. 



Pasteur wished to go further ; he was now beginning to 

 study the crystallizations of formate of strontian. Comparing 

 them with those of the paratartrates of soda and ammonia, 

 surprised and uneasy at the differences he observed, he once 

 exclaimed, " Ah ! formate of strontian, if only I had got you ! " 

 to the immense amusement of Bertin, who long afterwards 

 used to repeat this invocation with mock enthusiasm. 



Pasteur was about to send these crystals to Biot, but the 

 latter wrote, "Keep them until you have thoroughly investi- 

 gated them. . . . You can depend on my wish to serve you in 

 every circumstance when my assistance can be of any use to 

 you, and also on the great interest with which you have 

 inspired me." 



Regnault and Senarmont had been invited by Biot to 

 examine the valuable samples received from Strasburg, the 

 dextroracemic and kevoracemic acids. Biot wrote to Pasteur, 

 " We might make up our minds to sacrifice a small portion of 

 the two acids in order to reconstitute the racemic, but we doubt 

 whether we should be capable of discerning it with certainty by 

 those crystals when they are formed. You must show it us 

 yourself, when you come to Paris for the holidays. Whilst 

 arranging my chemical treasures, I came upon a small quantity 

 of racemic acid which I thought I had lost. It would be 

 sufficient for the microscopical experiments that I might 

 eventually have to make. So if the small phial of it that you 

 saw here would be useful to you, let me know, and I will 

 willingly send it. In this, as in everything else, you will 

 always find me most anxious to second you in your labours." 



This period was all happiness. Pasteur's father and his 

 sister Josephine came to Strasburg. The proposal of marriage 

 was accepted, the father returned to Arbois, Josephine stay- 

 ing behind. She remained to keep house and to share the 

 everyday life of her brother, whom 6he loved with a mixture of 



