Still under the hallucination caused by the Galenical theories, anatomists thought that both lacteals and thoracic duct could be traced to the liver. Rudbeck discovered the general lymphatics in 1651.
A clearer idea of the gross anatomy of the brain, especially of its internal cavities, was due to the descriptions of Francis Boë, usually known as Franciscus Sylvius (1614-72), professor at Leyden, whose name survives in the aqueduct, fissure, fossa, and artery of Sylvius. The science of chemistry was at this time gradually emerging from the superstitions of alchemy, and Sylvius is also famous for being among the first to attempt to differentiate the structures and fluids of the body by means of their chemical reactions. Vieussens (1641-1715) of Montpellier also increased the knowledge of the nervous system, both central and peripheral, describing the anterior pyramids, the olive, and the anterior medullary velum which sometimes bears his name. To Thomas Willis (1622-75) (q.v. ) of London, sometime professor at Oxford, is due a systematic description of the brain and its cavities, together with a classification of the cranial nerves in which he finally separated the sympathetic cord from that series. He recognized that the brain becomes gradually more complicated as we ascend the animal scale, and that it is more easily understood by a study of the lower and more simple forms. The decussation of the pyramids was first described by Duverney (1648-70), demonstrator at the Jardin du Eoi, afterward the Jardin des Plantes. at Paris. The doctrine of the "animal spirits," supposed to fill the ventricles of the brain and to be distributed by the nerves, was first seriously attacked by Wepffer (1658).
The advance of the physical sciences instituted by Galileo (1564-1642) had a profound effect upon anatomy. The new developnents in optics were now called on to contribute to the problems of structure. The optical properties of the crystalline lens were now described by Kepler (1571-1630) (q.v.), the eminent astronomer, who denied that it is the seat of vision as supposed by Hippocrates : the image on the retina was demonstrated by Scheiner (1575-1650); Descartes (1596-1650) showed the eye to be a camera obscura, and suggested that accommodation is produced by a change in the convexity of the lens. He also made some very acute observations on the structure and functions of the nervous system. marred, however, by metaphysical speculations that were attacked by Stensen, who declared that in order to determine the functions of organs we must first ascertain their structure.
A new instrument of research which the Ital- ians, impelled by the zeal imparted by Galileo, were the first to apply to scientific uses, was now introduced. Tliis was the microscope, hitherto merely an optical curiosity. The magnifying power of convex lenses was known to the an- cients, for even in the ruins of Nineveh a pol- ished rock crystal lens has been found, and there is good reason to believe that similar instruments were used in ancient Egypt and in Greece. Spectacles were used in Europe .as early as the thirteenth century, and the compound mi- croscope was invented about 1590 by Hans and Zacharias Janssen of Middelhurg. Holland. No means for correcting chromatic and spherical aberration being then known, the first instru- ments were clumsy and imperfect ; consequently, ma-ny investigators preferred to use the simple microscope, especially after Leeuwenhoek had shown what excellent results could be obtained with small but accurate lenses.
Among the first and most acute observers was Jlarcello Malpighi (1628-94), professor at Bo- logna, Pisa, and Messina, a man of extraordinary acuteness of intellect, combined with an indom- itable zeal for natural research. He left his mark in almost all departments of biology. He was an accomplished botanist, and by his re- searches among plants laid the foundations of the modern cell-theory; he was an entomologist, devoting himself to an exhaustive study of the anatomy and development of the silk-worm ; he was an embryologist, being the first to build upon the incomplete studies of Harvey and Fab- ricius and describe adequately the changes of the chick in the egg ; he was a pathologist, studying carefully post - mortem appearances and the causes of disease; he was also a compar- ative anatomist, drawing many of his conclu- sions as to the structure of man from an exam- ination of animals.
Before Malpighi's time but little was known regarding the structure of glands. Under this designation were included many non-glandular organs, like the tongue and the brain, the latter being supposed to secrete not only the animal spirits but the nasal mucus or pituita which was believed to pass down through holes in the cribriform plate of the ethmoid bone. Sylvius had, it is true, distinguished as conglomerate glands aggregations like the pancreas and the salivary glands, and as conglobate glands those of the lymphatic system. The ducts of some of the larger glands were unknown, the liver was considered a great blood-making organ that received the bile elaborated by the gall-bladder for the purpose of combining it with the blood, and the mechanism of secretion was wholly misunderstood. Wii'sung discovered the pancreatic duct in 1642, but supposed it to be a lymphatic leading to the liver ; Wharton described the submaxillary duct in 1652; Stensen the parotid duct (previously thought to be a tendon) in 1661; Bartholin the sublingual duct; Bellini the straight tubules of the kidney in 1662; Peyer the closed follicles of the intestines in 1677, and Brunner the duodenal glands in 1682. Schneider (1614-80), professor at W^ittenberg, finally described the pituitary membrane of the nasal passages and settled the origin of the nasal mucus. It was JIalpighi, however, who first united these scattered observations and gave a clear idea of the structure of acinous glands. It was during his researches on tliis subject that he discovered the acinous structure of the lung, and demonstrated that there are no visible orifices by which air can pass from the vesicles into the pulmonary veins. Here, too, he first observed, in the lung of the frog, the capillary blood vessels "distributed in a ring-like fashion," thus justifying Harvey and forever settling the question of the circulation of the blood. He described most of the structure of the kidney as it is known to us to-day. and in the spleen discovered the bodies that bear his name. He saw and described the red blood corpuscles, unaware that they had been previously discovered ly Swanunerdam, a Dutch anatomist, in 1658. "Extending his researches to the skin, he discovered the rete mucosum, or Malpighian
