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26 drawing, afterwards published by Blasius; and states the result of his inquiries in a letter to Thevenot, in the following particulars: 1. The Spinal Marrow consists entirely of fibres. 2. Those distinct fibres meet and terminate in some part of the brain. 3. Fibrous nerves issue from the fibres of the spinal marrow. 4. The pia mater is altogether extended into hollow sheaths. 5. All these things may be easily seen by suddenly placing the yet warm spinal marrow along with the vertebrae containing it in cold water, and breaking the vertebrae with great caution from the marrow, after having suffered both to remain in that situation during the space of a day and a night. After composing an elaborate essay on Respiration as a thesis, he repaired to Leyden to take his degree. There he resumed his intimacy with the famous Van Horne, under whom he had formerly studied. Aware of his extraordinary skill in such matters, this Professor engaged him in a variety of experiments, and in forming anatomical preparations, for which he took care to supply him with abundance of materials; and with such enthusiasm did the young physician prosecute this congenial task, that he is said to have laboured both by night and day. It was on this occasion that he first injected the uterine vessels of a human subject with a ceraceous matter, a useful operation which he subsequently learned to perform with great accuracy and beauty. He now also began to practice a new and excellent method of preparing delicate viscera for demonstrations, namely,