Before Nalpighi'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 crib riform 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 re ceived the bile elaborated by the gall-bladder for the purpose of combining it with the blood, and the mechanism of secretion was wholly misun derstood. Wirsung discovered the pancreatic duet 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 1602; fever the closed follicles of the intestines in 1077, and Brunner the duodenal glands in 1682. Schneider (1614-S0), professor at Wittenberg, finally described the pituitary membrane of the nasal passages and settled the origin of the nasal mucus. It. was Malpighi, however, who first united these scattered observations and gave a clear idea of the structure of aeinous glands. It was during his researches on this subject that he discovered the aeinous 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. Ile described most of the structure of the kidney as it is known to us to-day, and in the spleen discovered the bodies that hear his name. He saw and described the red blood corpuscles, unaware that they had been previously discov ered by Swannuerdam, a Dutch anatomist, in 1058. his researches to the skin, he discovered the rete mucosum, or Malpighian layer, and the papilla', which he surmised were organs of touch. He elucidated the structure of the liver, which Glisson (1597-1677), pro fessor at Cambridge, had already carefully de scribed, showing that it is an acinous gland of peculiar construction, and, by tying the bile duct. demonstrated that the bile is formed in the liver and not in the gall-bladder.
As a consequence of the increase of the power of vision by the use of the microscope, the phe nomena of fecundation and the development of the embryo began to receive attention. Sper matozoa were discovered in 1677 by a pupil of Loeuwenhoek, and De Graaf, discovering the ovi sacs (Graafian follicles) about 1672, supposed them at first to be ova. Naboth, too, discovering the closed follicles of the neck of the uterus, supposed them to be ova (Ocala Nabothi). The ova of the lower vertebrates were, of course, well known, and the phenomena of their devel opment were specially investigated by Malpighi. Van Horne, of Leyden. probably saw the human ovum in 1668, but it was not unmistakably rec ognized until Von Bbr demonstrated it in 1827.
During the course of this investigation two schools arose—the Animaleulists and the Ovists, that respectively maintained the superior effi cacy of the male or female elements. Attempts were made to explain the transmission of heredi tary qualities from parent to child. Aristotle, having studied the development of the egg, had declared that the embryo primitively consisted of simple, undifferentiated material, from which, by successive stages, the adult was formed (the ory of post-formation or epigem=sis). Opposed to this was another contention, that either the male or the female elements must possess in miniature all the organs of the adult (theory of preformation).
A further result of microscopic research was an enlarged view as to the distribution of living things. The discovery by Leeuwenhoek (1632 1723) that organic infusions soon become replete with living forms when exposed to the air, led to the revival of the ancient notion of the spon taneous generation of living from non-living matter. This led to fanciful theories regarding fecundation that were not overthrown until Spallanzani (1729-99) showed that living forms do not develop in infusions that have been boiled and then excluded from the air, and that filtered seminal fluid has lost the power of impregnation. Following up the researches of llartsoeker (1656 1725) he also demonstrated that ordinary air teems with living particles that enter the human body and pass into infusions. This doctrine was termed panspermatism, and developed after ward into the modern "germ theory," which has had a profound influence upon pathological anat omy.
The following discoveries of this period may lie briefly noted: Ole Worm (158S-1654), pro fessor at Copenhagen. discovered the interealary bones of the skull ; Clopton Havers of England, in 1692, the Haversian canals and the intimate structure of hone; Hooke (1635-1703), the prim itive fibrilhe of muscle: Kerkring (1640-93), the valvulm conniventes of the small intestine; Win slow (1669-1 760) , of Paris, the foramen con necting the two cavities of the peritoneum; Douglas (1675-1742), of London, the recto-uter ine pouch and several other features of the peri toneum and the abdominal wall.
The classification of animals by their anatom ical structure, attempted first by Aristotle, was revived by several authors during the eighteenth century, and notably by Karl von Linne (Lin IITUS) of in Sweden (1707-78), who considered that each particular species was im mutably established at the creation, man being placed• at the head in the order Primates. Buffon (1707-SS), however, supposed that varia tions occur from changes of environment, and even hinted that all species may have origi nated from a primitive common stock. This was afterward more boldly advocated by Lamarck (1744-1829), who was the first to maintain sys tematically the mutability of species, and to look upon man as derived from a common stock with other organisms, conceiving that the ancestral record of all might be represented as a branching tree. To this was opposed the authority of the great comparative anatomist Cuvier (1769-1832), who caused these views to sink into obscurity for a time.