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Updated: June 25, 2025
And this statement has since received full confirmation from Pasteur. On the other hand, Schwann, Schroeder and Dusch, and Pasteur, have amply proved that air may be allowed to have free access to beer-wort, without exciting fermentation, if only efficient precautions are taken to prevent the entry of particles of yeast along with the air.
A century and a half elapsed, and the investigation of yeast was recommenced almost simultaneously by Cagniard de la Tour in France, and by Schwann and Kützing in Germany. The French observer was the first to publish his results; and the subject received at his hands and at those of his colleague, the botanist Turpin, full and satisfactory investigation.
As the title suggests, the main idea that actuated Schwann was to unify vegetable and animal tissues. Accepting cell-structure as the basis of all vegetable tissues, he sought to show that the same is true of animal tissues, all the seeming diversities of fibre being but the alteration and development of what were originally simple cells.
Adopting this name, Schwann propounded what soon became famous as his cell theory, under title of Mikroskopische Untersuchungen uber die Ubereinstimmung in der Structur und dent Wachsthum der Thiere und Pflanzen. So expeditious had been his work that this book was published early in 1839, only a few months after the appearance of Schleiden's paper.
Consider that the labours of Laplace, of Young, of Davy, and of Faraday; of Cuvier, of Lamarck, and of Robert Brown; of Von Baer, and of Schwann; of Smith and of Hutton, have all been carried on since Priestley discovered oxygen; and consider that they are now things of the past, concealed by the industry of those who have built upon them, as the first founders of a coral reef are hidden beneath the life's work of their successors; consider that the methods of physical science are slowly spreading into all investigations, and that proofs as valid as those required by her canons of investigation are being demanded of all doctrines which ask for men's assent; and you will have a faint image of the astounding difference in this respect between the nineteenth century and the eighteenth.
And when Schwann put forward the explicit claim that "there is one universal principle of development for the elementary parts, of organisms, however different, and this principle is the formation of cells," he enunciated a doctrine which was for all practical purposes absolutely new and opened up a novel field for the microscopist to enter.
They consist of a rod, or central core, continuous throughout the whole length of the nerve, called the axis cylinder. This core is surrounded by the white substance of Schwann, or medullary sheath, which gives the nerve its characteristic ivory-white appearance. The whole is enclosed in a thin, delicate sheath, known as neurilemma.
In his famous "Mikroskopische Untersuchungen" Schwann speaks of Torula as a "cell"; and, in a remarkable note to the passage in which he refers to the yeast plant, Schwann says:
Of course various other workers at once disputed Schwann's claim to priority of discovery, in particular the English microscopist Valentin, who asserted, not without some show of justice, that he was working closely along the same lines. Put so, for that matter, were numerous others, as Henle, Turpin, Du-mortier, Purkinje, and Muller, all of whom Schwann himself had quoted.
He believed the Marquis to be dead, and was finally able to tell his story. Schwann began to be very anxious. Where was Fanfar? Suddenly a horse was heard coming at full speed. Schwann and Caillette rushed to the door. They uttered a simultaneous cry of surprise. It was the Marquis. "And Fanfar? Where is he?" "He is coming. But I have not a moment to lose. Take me to Gudel's chamber."
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