Artropods and Human Disease 24 page

Suddenly Coleman thought of his own father, his strong suspicion that the sensitized blood which killed the Alexanders’ child had stemmed from a transfusion his father had given years before—given without Rh typing, even though the dangers were already known to medicine.

“Yes,” he said. “I suppose it does.”

Both men had risen and moved to the door. As they went out O’Donnell said softly, “It’s a good thing for all of us to have compassion. You see, you never know whether someday you’ll need it yourself.”

Lucy Grainger said, “Kent, you look tired.”

It was early afternoon, and O’Donnell had paused in a main-floor corridor. Unnoticed, she had stopped beside him.

Dear Lucy, he thought—unchanged, warm and tender. Was it really less than a week ago that he had considered leaving Burlington and marrying Denise? At the moment it all seemed far away—a nostalgic interlude that now was nothing more. Here was where he belonged; in this place, for good or ill, was where his destiny lay.

He took her arm. “Lucy,” he said, “let’s meet soon. There’s a lot we have to talk about.”

“All right.” She smiled with affection. “You may take me to dinner tomorrow.”

Side by side, they moved on down the hallway, and it was somehow reassuring to have her beside him. He glanced sideways at her profile, and there came to him a sense of certainty that for both of them there was much that was good ahead. Perhaps it would take time to adjust, but in the end he knew they would find their future together.

Lucy was thinking: Dreams do come true; perhaps mine will—someday soon.

Dusk came early to Pathology. It was a price they paid for working in the hospital basement. Snapping lights on, David Coleman decided that one of his early projects would be to move the department to a better location. The day when pathologists were automatically relegated to the bowels of the hospital was over; light and air were as much requisites for them as for any other branch of medicine.

He entered the pathology office and found Pearson at his desk. The old man was emptying the contents of the drawers. He looked up as Coleman came in.

“It’s a funny thing,” he said, “how much junk you can accumulate in thirty-two years.”

For a moment David Coleman watched. Then he said, “I’m sorry.”

“Nothing to be sorry about.” Pearson answered gruffly. He closed the last drawer and put papers in a case. “I hear you’re getting a new job. Congratulations.”

Coleman said, and meant it, “I wish it could have been some other way.”

“Too late to worry now.” He snapped the locks on the case and looked around. “Well, I guess that’s everything. If you find anything else you can send it with my pension check.”

“There’s something I want to tell you,” Coleman said.

“What’s that?”

Coleman spoke carefully. “The student nurse—the one who had her leg amputated. I dissected the limb this morning. You were right. I was wrong. It was malignant. Osteogenic sarcoma without a doubt.”

The old man paused. He gave the impression that his thoughts were far away. “I’m glad I didn’t make a mistake,” he said slowly, “about that anyway.”

He picked up a topcoat and moved to the door. He seemed about to go, then turned back. Almost diffidently he asked, “Do you mind if I give you some advice?”

Coleman shook his head. “Please do.”

“You’re young,” Pearson said. “You’re full of spice and vinegar—that’s good. You know your stuff too. You’re up to date—you know things that I never did, never will now. Take my advice and try to keep it that way. It’ll be tough to do; make no mistake about it.” He waved toward the desk he had just vacated. “You’ll sit ha that chair and the phone will ring, and it’ll be the administrator—talking about budgets. Next minute one of the lab staff will want to quit; and you’ll have to smooth that out. And the doctors will come in, and they’ll want this bit of information and that.” The old man smiled thinly. “Then you’ll get the salesman—the man with the unbreakable test tube and the burner that never goes out. And when you’re through seeing him there’ll be another and another and another. Until at the end of a day you’ll wonder what happened to it and what you’ve accomplished, what you’ve achieved.”

Pearson stopped and Coleman waited. He sensed that in his words the old pathologist was reliving a part of his own past. He went on, “That’s the way the next day can go, and the next, and the one after that. Until you find a year has slipped by, and another, and another. And while you’re doing all this you’ll send other people on courses to hear about the new things in medicine—because you can’t take time out to go yourself. And you’ll quit investigation and research; and because you work so hard, you’ll be tired at night, and you won’t feel like reading textbooks. And then suddenly, one day, you’ll find everything you knew is out of date. That’s when it’s too late to change.”

Emotion-charged, the voice faltered. Pearson put a hand on Coleman’s arm. He said imploringly, “Listen to an old man who’s been through it all, who made the mistake of falling behind. Don’t let it happen to you! Lock yourself in a closet if you have to! Get away from the phone and the files and paper, and read and learn and listen and keep up to date! Then they can never touch you, never say, ‘He’s finished, all washed up; he belongs to yesterday.’ Because you’ll know as much as they do—and more. Because you’ll have experience to go with it . . .”

The voice trailed off and Pearson turned away.

“I shall try to remember,” Coleman said. He added gently, “I’ll come with you to the door.”

They climbed the stairs from Pathology, and on the hospital’s main floor the bustle of early-evening activity was just beginning. A nurse passed them hurriedly; she carried a diet tray, her starched uniform swishing. They moved aside to let a wheel chair by; in it was a middle-aged man, one leg in a cast, holding a pair of crutches like oars withdrawn into a boat. A trio of student nurses went past laughing. A Women’s Auxiliary worker propelled a cart with magazines. A man clutching a bouquet of flowers headed for the elevators. Somewhere out of sight a child was crying. It was the hospital world: a living organism, a mirror of the greater world outside.

Pearson was looking around him. Coleman thought: Thirty-two years, and he’s seeing it all, perhaps for the last time. He wondered: How will it be when my own time comes? Shall I remember this moment thirty years from now? Will I understand it better then?

On the public-address system a voice announced, “Dr. David Coleman. Dr. Coleman to the surgical floor.”

“It’s started,” Pearson said. “It’ll be a frozen section—you’d better go.” He held out his hand. “Good luck.”

Coleman found it hard to speak. “Thank you,” he said.

The old man nodded and turned away.

“Good night, Dr. Pearson.” It was one of the senior nurses.

“Good night,” Pearson said. Then, on the way out, he stopped under a “No Smoking” sign to light a cigar.

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Artropods and Human Disease

The Arthropoda is the largest phylum, containing more than 80% of all animal life.

Arthropods directly cause or transmit more than 80% of all diseases.

Arthropods are bilaterally symmetrical, coelomate and metamerically segmented animals.

Each typical segment generally bears a pair of stout, jointed appendages, of which at least one pair functions as jaws.

The body is covered by a chitinous exoskeleton, which undergoes periodic moulting.

Muscles are mostly striped and they do not form continuous layers.

Coelom is much reduced and the perivisceral cavity is a haemocoele.

Circulatory system is open.

Sexes are generally separated.

Digestive, respiratory, excretory, and nervous systems are present.

The Phylum Arthropods contain many members and are divided into five classes.

Three classes (Crustacea, Arachnida and Insecta) contain most of the medically important arthropods.

Life Cycle

All Arachnida and most Insecta develop from egg to adult by a process called metamorphosis. Incomplete metamorphosis has three stages: egg, nymph, and imago, the sexually mature adult. The nymph, resembling a miniature adult, emerges from the eggs and molts several times before it becomes an imago. After each molt, the nymphal form is called an instar.

Wings of flying insects increase in size with each instar.

Lice, true bugs (Hemiptera), and arachnids develop through incomplete metamorphosis.

Complete metamorphosis has the, egg, larva pupa, and imago stages. An insect larva emerges from the egg as a segmented wormlike larva and matures through a series of larval instars until finally enclosing itself inside a pupa casing. After a time, the transformed imago emerges.

Flies, mosquitoes, and fleas develop through complete metamorphosis.

Development of most crustaceans is by incomplete metamorphosis; however, the names of the stages are different. Eggs hatch and release free-swimming nauplius larvae that molt several times to become mature adults. However, some species undergo complete metamorphosis; the nauplius develops into a cypris larva (a stage similar to the pupa), and the transformed larva emerges as an adult.

Date: 2014-12-21; view: 723