As the distance and expense made it impossible for Agassiz to spend his vacations with his family in Switzerland, it soon became the habit for him to pass the holidays with his new friend at Carlsruhe. For a young man of his tastes and acquirements a more charming home-life than the one to which he was here introduced can hardly be imagined. The whole atmosphere was in harmony with the pursuits of the students. The house was simple in its appointments, but rich in books, music, and in all things stimulating to the thought and imagination. It stood near one of the city gates which opened into an extensive oak forest, in itself an admirable collecting ground for the naturalist. At the back certain rooms, sheltered by the spacious garden from the noise of the street, were devoted to science. In the first of these rooms the father's rich collection of minerals was arranged, and beyond this were the laboratories of his sons and their friends, where specimens of all sorts, dried and living plants, microscopes and books of reference, covered the working tables. Here they brought their treasures; here they drew, studied, dissected, arranged their specimens; here they discussed the theories, with which their young brains were teeming, about the growth, structure, and relations of animals and plants.* (* See "Biographical Memoir of Louis Agassiz" by Arnold Guyuot, in the "Proceedings of U.S. National Academy".)
From this house, which became a second home to Agassiz, he wrote to his father in the Christmas holidays of 1826:. . ."My happiness would be perfect were it not for the painful thought which pursues me everywhere, that I live on your privations; yet it is impossible for me to diminish my expenses farther. You would lift a great weight from my heart if you could relieve yourself of this burden by an arrangement with my uncle at Neuchatel. I am confident that when I have finished my studies I could easily make enough to repay him. At all events, I know that you cannot pay the whole at once, and therefore in telling me frankly what are our resources for this object you would do me the greatest favor. Until I know that, I cannot be at peace. Otherwise, I am well, going on as usual, always working as hard as I can, and I believe all the professors whose lectures I attend are satisfied with me.". . .His father was also pleased with his conduct and with his progress, for about this time he writes to a friend, "We have the best possible news of Louis. Courageous, industrious, and discreet, he pursues honorably and vigorously his aim, namely, the degree of Doctor of Medicine and Surgery."
In the spring of 1827 Agassiz fell ill of a typhus fever prevalent at the university as an epidemic. His life was in danger for many days. As soon as he could be moved, Braun took him to Carlsruhe, where his convalescence was carefully watched over by his friend's mother. Being still delicate he was advised to recruit in his native air, and he returned to Orbe, accompanied by Braun, who did not leave him till he had placed him in safety with his parents. The following extracts from the correspondence between himself and Braun give some account of this interval spent at home.
AGASSIZ TO BRAUN.
ORBE, May 26, 1827.
. . .Since I have been here, I have walked faithfully and have collected a good number of plants which are not yet dry. I have more than one hundred kinds, about twenty specimens of each. As soon as they can be taken out of the press, I'll send you a few specimens of each kind with a number attached so that you may identify them. Take care that you do not displace the numbers in opening the package. Should you want more of any particular kind let me know; also whether Schimper wishes for any. . .At Neuchatel I had the good fortune to find at least thirty specimens of Bombinator obstetricans with the eggs. Tell Dr. Leuckart that I will bring him some,—and some for you also. I kept several alive laid in damp moss; after fourteen days the eggs were almost as large as peas, and the little tadpoles moved about inside in all directions. The mother stripped the eggs from her legs, and one of the little tadpoles came out, but died for want of water. Then I placed the whole mass of eggs in a vessel filled with water, and behold! in about an hour some twenty young ones were swimming freely about. I shall spare no pains to raise them, and I hope, if I begin aright, to make fine toads of them in the end. My oldest sister is busy every day in making drawings for me to illustrate their gradual development. . .I dissect now as much and on as great a variety of subjects as possible. This makes my principal occupation. I am often busy too with Oken. His "Natur-philosophie" gives me the greatest pleasure. I long for my box, being in need of my books, which, no doubt, you have sent. Meantime, I am reading something of Universal History, and am not idle, as you see. But I miss the evenings with you and Schimper at Heidelberg, and wish I were with you once more. I am afraid when that happy time does come, it will be only too short. . .
BRAUN TO AGASSIZ.
HEIDELBERG, May, 1827.
. . .On Thursday evening, the 10th, I reached Heidelberg. The medical lectures did not begin till the second week of May, so that I have missed little, and almost regret having returned so soon. . . I passed the last afternoon in Basel very pleasantly with Herr Roepper, to whom I must soon write. He gave me a variety of specimens, showed me many beautiful things, and told me much that was instructive. He is a genuine and excellent botanist, and no mere collector like the majority. Neither is he purely an observer like Dr. Bischoff, but a man who thinks. . .Dr. Leuckart is in raptures about the eggs of the "Hebammen Krote," and will raise them. . .Schweiz takes your place in our erudite evening meetings. I have been lecturing lately on the metamorphosis of plants, and Schimper has propounded an entirely new and very interesting theory, which will, no doubt, find favor with you hereafter, about the significance of the circular and longitudinal fibres in organisms. Schimper is fruitful as ever in poetical and philosophical ideas, and has just now ventured upon a natural history of the mind. We have introduced mathematics also, and he has advanced a new hypothesis about comets and their long tails. . . Our chief botanical occupation this summer is the careful observation of all our plants, even the commonest, and the explanation of whatever is unusual or enigmatical in their structure. We have already cracked several such nuts, but many remain to be opened. All such puzzling specimens are spread on single sheets and set aside. . .But more of this when we are together again. . .Dr. Leuckart begs you to study carefully the "Hebammen Unke;"* (* Bombinator obstetricans referred to in a former letter.) to notice whether the eggs are already fecundated when they are in the earth, or whether they copulate later in the water, or whether the young are hatched on land, and what is their tadpole condition, etc. All this is still unknown. . .